Among the defining features of post-Saturn Sega was their proprietary GD-ROM technology. Although trailblazing the arcade market and expanding into enhanced ports on Windows PCs kept Sega afloat as a company, the financial bath precipitated by their 32-bit home console failures left them in a dilemma. Sony, like NEC in the 4th console generation before them, was an electronics giant who could afford to invest in whatever new ventures they chose; while NEC lost their console war venture and opted to drop out at the end of it, Sony won theirs and was poised to aggressively pursue a repeat performance at the expense of Sega's further participation. The story of Dreamcast as Sega's last home console gambit is well-documented elsewhere, but Sega would play a big part in keeping arcades alive as their popularity continued to fade into a fraction of what they were in the golden age.
This time around, more than before, Sega's arcade technology bore close relationship to home consoles with a new twist. Dreamcast ushered in the 6th console generation but was also the first knocked out of it, at which point Sega went 3rd party and would work with new allies for further developments. Arcade games continued to be stronger technologically but this era was the last and biggest defined by basis in home consoles, Sega or otherwise.
NAOMI (1998-2006)
The New Arcade Operation Machine Idea followed in the footsteps Sega Titan/ST-V had with Saturn by matching Dreamcast, especially the GD-ROM variant that enabled higher storage than traditional ROM boards. Of course, this meant NAOMI games ported exceptionally well to Dreamcast thus any of those are usually the most accessible means of experiencing them, and wherever that isn't possible Dreamcast emulators tend to be cross-compatible with the ROMs of these arcade systems. The original variant remained Sega's flagship for a good long time, all the way to the end of the era today's post covers...
F1 World Grand Prix: Sega arcade systems had always been available to other companies in one form or another but this game, developed by Video Systems, was first of many to really ramp up on the trend (it helped it was concurrently developed for Dreamcast too)
The House of the Dead 2: the most ported and re-released game in the series by far and the basis for its first Typing spin-off
Power Stone: a fighter by Capcom and Dreamcast launch title in the US, re-releases aside the short-lived series was exclusive to Sega hardware
Charge 'N Blast: a 3D shoot-'em-up not held in as high regard as other classics of the time which could explain why it never got a port other than Dreamcast
Crazy Taxi: the driving game known for its content changes in multiple re-releases over the years making the arcade original and its Dreamcast port still the favorite of many fans (though it should be noted that the PlayStation 2 and GameCube ports match Dreamcast content)
Airline Pilots: premiere title in the Sega Professional series which were as much simulation as game, this was apparently the least popular since flying a large passenger plane is something that only appeals to a niche
Zombie Revenge: a similar theme to House of the Dead but in 3rd-person perspective, it remains known as a classic in the early Dreamcast library (which is still full of exclusives such as this title)
Ring Out 4x4: although this top-down vehicular combat game remained in Japan it's still notable as the first original game produced by Sega's Mechatronics division which beforehand (consisting of what were previously known as AM4 and AM6) focused on arcade hardware rather than game production
Virtua Striker 2 Ver. 2000: while this subvariant is arcade-exclusive it also got a 2000.1 update specifically made for Dreamcast
F355 Challenge: known by various names in its ports and re-releases, this is possibly the most simulation Yu Suzuki has gone with any of his racing games and has a learning curve to match; it has a PlayStation 2 as well as Dreamcast version
Derby Owners Club: multiplayer-focused virtual racing horse trainer that premiered the Satellite Terminal NAOMI variant (no other games for that specific system will be covered here; all were Japan-exclusive)
Jambo! Safari: the second in the Sega Professional series for NAOMI (the series was on other hardware such as Emergency Call Ambulance for Model 3), it took a decade to come home on Nintendo systems
Toy Fighter: while the Dreamcast port was cancelled there was a US release of this arcade game
World Series 99: not only was this the premiere of Sega's exceptional home console baseball simulator for arcades (though in Japan it was considered a continuation of the long-running Super League series) but a 1999 edition for arcade filled the gap between 98 for Saturn and 2K1 for Dreamcast
Dead or Alive 2: though Sega was only involved in the arcade and Dreamcast versions, this was part of a longer-running collaboration with Tecmo that would culminate years later in a Virtua Fighter crossover; a Millennium edition released the following year bring to arcade features made for the Dreamcast port
Sega Tetris: even though it was still Japan-exclusive and arcade-focused Sega had the foresight to keep their unique variant alive with new entries in case it paid off or them
Outtrigger: a first-person shooter (crossing into run-and-gun territory) by Yu Suzuki, it didn't get ported to Dreamcast until later in the system's life but is still fondly-remembered
18 Wheeler American Pro Trucker: by far the most popular in the Sega Professional series it got ports to PlayStation 2 and GameCube (as well as Dreamcast) and a sequel
Samba de Amigo: Sonic Team was deep into genre experimentation in the latter half of the 90s and this unique maraca-based rhythm game serves as proof, unfortunately the later Ver. 2000 edition never left Japan in any form; while the Dreamcast port was best-played with the fairly rare and expensive maraca controllers, the hand motion control basis made it's later Nintendo Wii version seem like a natural fit
Virtua Tennis: despite the name this was not an AM2 product but rather made by AM3 and it started a series that fell more at home in consoles than the arcades; ported to Windows PC (a trend for the series) as well as Dreamcast, the latter edition is known for its quirky support of quasi-motion controls through Dreamcast's fishing controller (which was apparently unintentional)
Ninja Assault: while Capcom was a close Sega ally in the Dreamcast era Namco was arguably more so in the arcade, something that would become more pertinent later
WWF Royal Rumble: among the final games for the license before changing their name to WWE, it was exclusive to US arcades and only went worldwide on Dreamcast
Giga Wing 2: while the prequel also got a Dreamcast port its arcade original was on Capcom hardware but this time with NAOMI it got on both
Capcom vs. SNK: the original was published in standard NAOMI form and on Dreamcast worldwide but its Pro upgrade was for NAOMI GD-ROM and its Dreamcast port remained in Japan
Cannon Spike: although developed by Psikyo it was published by Capcom for NAOMI and Dreamcast
Project Justice: its prequel Rival Schools was made for the PlayStation-based ZN-2 arcade system thus its PlayStation port was spot-on; for this game the same parallel would occur with NAOMI and Dreamcast
Virtua NBA: Sega was no stranger to the NBA license but this game proved it could never match the arcade approach of Midway and best stuck with sports simulations for home consoles
Spawn: In the Demon's Hand: yet another example of how much of a friend Capcom was to Sega at this time as its home version was once again exclusive to Dreamcast
The Typing of the Dead: a typing trainer for the arcade was bizarre enough for the arcade original to stay in Japan; while the Dreamcast port is fine enough its requirement to have the keyboard accessory, while such would have been no issue for those already browsing with the system's PlanetWeb, still makes the later PC version the most accessible
Sega Marine Fishing: the only NAOMI version of the fishing series (which had its entirety on Dreamcast) it is less simulation and more arcade
Marvel vs. Capcom 2: like other Capcom franchise games the prequel had a port to a Sega console but debuted on Capcom hardware, now the sequel opts to make NAOMI its arcade home
Power Stone 2: this sequel was also exclusive to Sega arcade and home hardware
Virtual-On Oratorio Tangram M.S.B.S. Ver. 5.66: the last and most revised of this second in the series that previously in arcades was on Model 3, it served as the basis for the later Xbox 360 port
Slashout: debut of the Spikeout series on NAOMI it at least had a US release
StarHorse: Sega Mechatronics opted to craft a whole new horse racing simulation that spawned its own long-running but Japan-exclusive series
Guilty Gear X: Arc System Works joins other third parties in embracing NAOMI for the 2nd in its fighting franchise, proving Sega at least scored itself a winner in designing developer-accessible hardware
Tokyo Bus Guide: whoever this Japanese exclusive was made for it did garner positive reviews
Crackin' DJ: first in a Japan-exclusive duology by Hitmaker (AM3) its sequel was likewise for NAOMI only
Death Crimson OX: the only arcade game in the Ecole-made series that completely and utterly failed to capture that House of the Dead spirit, all 3 titles are examples of games to be thankful never left Japan
Sega Strike Fighter: a NAOMI Multiboard title like F355 Challenge which used multiprocessing to gain extra power for such intense games, this was so much more popular than the premiere Airline Pilots that it was sold as a conversion kit for that game; nominally part of the After Burner series, unfortunately the lack of a home conversion meant only arcades would see one of the last video games to include being able to fly around a New York City still endowed with the Twin Towers of the original World Trade Center
Confidential Mission: a light gun shooter exclusive to the NAOMI GD-ROM variant in arcades, otherwise it and its Dreamcast port are not really that remarkable
Sports Jam: most sports games focus on a single sport, but this is a rare multi-sport variant and was also on Dreamcast for those interested in a more "bite-size" experience somewhat akin to Wii Sports without the cartoony graphics
Shakatto Tambourine!: like Samba de Amigo but with tambourines rather than maracas, while released only in Japan its claim to unique fame is being the only Sega arcade game to receive a home port to (of all consoles) the original PlayStation
Gun Survivor 2: despite the subtitle match this is not a port of Resident Evil CODE: Veronica but unique arcade collaboration between Capcom and Namco
F355 Challenge 2: a re-release that integrated content from the home console ports of the original (not an uncommon practice in this era) it was last of the original NAOMI Multiboard games and can be seen as the last of Yu Suzuki's several games than got an enhanced re-release billed as a sequel (others being After Burner and Galaxy Force)
Capcom vs. SNK 2: 2001 was the last year of Dreamcast and NAOMI dominance, meaning unlike this game's prequel the Sega hardware versions would remain exclusive to Japan
Zero Gunner 2: the sequel to Psikyo's Model 2 exclusive, this time it came home via Dreamcast (albeit in Japan only)
Cosmic Smash: this hearkening back to classic ball-and-paddle arcade games had limited distribution
Virtua Tennis 2: since this game already had professional licensing it was no stretch for the home ports being made part of Sega Sports 2K branding; the Dreamcast version ditched its prequel's quirk with the Fishing Controller while the PlayStation 2 edition debuted the franchise's close association with Sony consoles that would last until its end
WaveRunner GP: finish of the duology that preimered on Model 2
Heavy Metal Geomatrix: Capcom crafted a fighter as one of the handful of games based on this comic property (another being an id Tech 3-powered shooter by Ritual Entertainment) that was experiencing a small resurgence in the early 2000s but must have fizzled-out quickly since the only home conversion was for Dreamcast
Alien Front: the arcade original remained in Japan, however Alien Front Online released for Dreamcast in the US only
Ikaruga: Treasure's successor to Radiant Silvergun paralleled Titan-Saturn by going NAOMI-Dreamcast, but the originals of both stayed in Japan for quite a while until the drought was broken with a worldwide re-release on Xbox Live Arcade
World Series Baseball: a finale in multiple ways, it concluded the long-running Super League series plus Sega's arcade exploration of the sport which started with Champion Baseball way back in 1983
Street Fighter Zero 3 Upper: the sole NAOMI (or any other Sega arcade system for that matter) version of Capcom's flagship fighting franchise landed by virtue as a re-release with content from the Dreamcast Street Fighter Alpha 3 which, by the name, was obviously was Japan-only
Lupin the 3rd: The Shooting: Japan-exclusive and based on the anime license but the game itself is still a Sega original that never got a home console version (although a Typing of the Dead-like variant would appear in arcades later)
Virtua Golf: last in a long line of Sega golf games, this simulator never left arcades but did release in the US
Monkey Ball: the arcade debut of a beloved action puzzle franchise that would continue solely on home consoles, the series would cut its teeth in Super Monkey Ball for Nintendo GameCube
Spikers Battle: the NAOMI GD-ROM final entry in the Spikeout series, at least for arcades since the only entry not stuck in Japan was the series finale released exclusively on Microsoft Xbox in 2005
Mazan: Flash of the Blade: a Namco release with a unique motion-sensitive samurai sword controller that played on a premise a lot like the 2013 reimagining of Shadow Warrior
Shootout Pool: a limited distribution arcade exclusive, so little information exists emulating it may be the only way to find out how well this billiards simulator plays
Virtua Athlete: a cut-down arcade edition of the Dreamcast's Virtua Athlete 2000, fun but does not seem a worthwhile alternative to the original home version
The Maze of the Kings: another Japan-exclusive light gun shooter by Hitmaker (AM3)
Puyo Puyo Fever: this is the point in the famed puzzle franchise original creator Compile had gone belly-up and it was now the domain of Sega's Sonic Team (AM8); the arcade edition and a plurality of home ports never made it to the US but the Nintendo GameCube and DS ones did as Puyo Pop Fever
Guilty Gear XX: third in the Arc Systems Works fighting franchise franchise was Japan-only for its arcade iteration but would be ported to PlayStation 2 in the West under the name Guilty Gear X2 (published by Sega parent company Sammy)
This is already a long list and not anywhere close to being exhaustive, however beyond 2003 the original NAOMI and its GD-ROM variant joined previous Sega console-based arcade in hosting simpler, re-hash and upgraded re-release games (including a 2007 reimagining of Dynamite Deka called Asian Dynamite). The hardware also powered the cores of several electromechanical, prize and medal games which were pretty much all Japan-exclusive. And this was the beginning of a line originally conceived as a budget-friendly alternative to the sophisticated but expensive Model 3.
Hikaru (1999-2001)
What was slated to succeed Model 3 is still part of the NAOMI family because the base core architecture is the same (uses the Hitachi SH-4 processor), but in a custom configuration made especially to draw out the power. Sound familiar? Yes, this author sees a major parallel with the Sega Saturn: indeed it is quite powerful though, while the individual components may be familiar enough, the combination thereof and the means by which they network makes for a system difficult for developers to exploit that power hence the short market time and game list...
Brave Firefighters: the hardware showcase for its sophisticated water effects, unsurprisingly this (not to mention the unique hose controller) pretty much preempted any possibility of a home port
Star Wars Racer Arcade: the third and [so far] last collaboration of Sega with LucasArts, its uniqueness is more lost today in light of enhanced digital re-releases of Star Wars Episode I Racer
NASCAR Arcade: the final collaboration (if you could even call it that) of Sega with Electronic Arts made necessary only because EA Sports had the license at the time
Planet Harriers: biggest and most unique entry in the Space Harrier series, this game alone is reason to attempt emulation of Hikaru since it never got a home port
Air Trix: skateboarding game a la Tony Hawk with Sega Mechatronics brought on board for the unique foot-operated controller
Virtual-On Force: while Japan-exclusive (even for its Xbox Live Arcade port) it did get a home adaptation of sorts in Virtual-On Marz for PlayStation 2 and that was released in America
NAOMI 2 (2001-2004)
Notice the logo has gone from red to Dreamcast orange? It would be simplistic to consider NAOMI 2 a re-standardized NAOMI Multiboard but in terms of what it offers that sums it up well. Both systems, for either their ROM board or GD-ROM variants, had interchangeability in mind and it was nice that owners of NAOMI 2 got backwards compatibility with the original on top of that. In fact that may have been the key factor in extending NAOMI's appeal since the successor only got a small fraction of the library size... Club Kart: go-kart racing can be just as appealing as any other kind but it's still rare and notable when a video game explores it; this never made it to homes but there is a US ROM
Virtua Striker 3: the third entry stayed consistent with its predecessor in that, while the actual numbered entry is arcade-exclusive, an minor updated variant was made for console which in this case is Virtua Striker 2002 for Nintendo GameCube
Wild Riders: something like Jet Set Radio with motorcycles (in appearance, not concept), it's arcade-only
Virtua Fighter 4: this entry in Sega's flagship fighting series had 3 variants (basic, Evolution, Final Tuned), all on NAOMI 2; the first two were ported to PlayStation 2 worldwide while the last was a smaller Japan-only update released soon before Virtua Fighter 5
Beach Spikers: AM2 at some point opted to explore the sport of beach volleyball, and for any interested home players it got a port with added features to GameCube
Sega Driving Simulator: the experience gained in the Sega Professional series paid off for public good, at least in Japan whose driving school criteria this was modeled for (but for most would make for a poor game)
The King of Route 66: successor to 18 Wheeler American Pro Trucker, it got a PlayStation 2 port
Initial D Arcade Stage: while the series debuted on Japanese Sega Saturn years prior, this racing series would continue for several entries on NAOMI 2 and beyond but sometime early in the Lindbergh era it stopped appearing anywhere other than Japan
Soul Surfer: nothing to do with the movie which was still years away (but is a recommended watch), this game's foot-operated surfboard controller was once again the design of Sega Mechatronics
Atomiswave (2003-2009)
Last and most cost-effective of the NAOMI family, this was originally conceived by Sammy (who owned Sega at the time) with Sega getting directly involved later. However, it would be a disservice to call this merely a cartridge-based Dreamcast variant: SNK, who had already worked with Sega in getting certain games for their Neo Geo Pocket handheld console games compatible with Dreamcast via a controller port link cable (near-identical to the setup Nintendo supported in their systems that generation), had discontinued their Neo Geo hardware series and adopted Atomiswave as successor. Accordingly, while it used Sega core hardware design it was less of a Sega system and more for Sammy and SNK with only one key exception...
Sega Bass Fishing Challenge: also happening to be the most recent core entry in the Sega Bass Fishing as well as the last Atomiswave game, it got ported to iOS in 2011 (which means incompatibility with any iDevice supported today)
Epilogue: Other Console-Based Systems (2002-2005)
Dreamcast may have been done but Sega wasn't, nor was their GD-ROM technology for cost-effectively loading a high capacity of data into RAM. Having cemented their alliance with Microsoft plus buried the hatchet with former rival Nintendo, Sega was poised for a technological exchange in the arcade market that would yield their last hurrah of console-based arcade systems that had been much of their bread & butter since the 80s. Aside from the GD-ROM drive and RAM upgrade, these boards were nigh-identical to the 6th generation home consoles from Nintendo and Microsoft (PlayStation 2 never received such a Sega treatment, though its core hardware later would be adapted for arcade by Konami and Namco).
What's interesting about the GameCube-based Triforce, at least so far as Sega is concerned, was logical hardware succession being met in a way. 1985, the same year Atari and Commodore did the same, was when Sega embraced the Motorola M68000 chipset that would define Sega hardware for over a decade. It happened to be that PowerPC was chosen in the 90s to succeed M68K; Sega was not involved in that succession whatsoever, preferring Hitachi processors for their 32-bit ventures, but through the PowerPC GameCube/Triforce they reaped a portion of the benefits anyway. Most Triforce games were Nintendo licensees, however Triforce is also the exclusive home of both editions of Virtua Striker 4.
The real portent of the future was the Xbox-based Chihiro, essentially a souped-up Windows PC by 2000 standards. Elsewhere on this blog has been written about how Xbox ought to be considered the home console successor to Dreamcast and that will not be reiterated here. Sega support for Chihiro and Xbox in turn (unsurprisingly, ports between the two were easy) was remarkable and the dawning of successful Xbox emulation gives hope that the few Chihiro exclusives can continue to be experienced (there exists a hack to alter one's Xbox console to play Chihiro games but only possible at a technical skillset beyond what yours truly is comfortable commenting on)...
The House of the Dead III: the one entry in the series opting for a Roman numeral, it is available on Xbox (bundled with its prequel), Nintendo Wii (again, bundled with its prequel), and PlayStation 3 digital-only download either separate or bundled with its sequel and spin-off
Crazy Taxi 3: High Roller: was ported to PC as well as Xbox but the latter is preferred for its soundtrack
Virtua Cop 3: this distant sequel remains arcade-exclusive hence the demand for emulation
OutRun 2: OK, THIS is a real distant sequel; the original edition got an enhanced port to Xbox while its SP upgrade got the same treatment multiplatform as OutRun 2006: Coast 2 Coast (the only Sega game supporting connectivity between PlayStation 2 and PlayStation Portable versions)
Ollie King: skateboard racing, not just performing; never ported to a home console but if Jet Set Radio Future vibes are detected that is actually no coincidence
Ghost Squad: beginning of a series though this was the only pre-Lindbergh entry; its sole home port was for Nintendo Wii
In 2005 (opening year for the 7th console generation) Sega launched the Lindbergh family, first of its PC-based arcade systems that continue today. In fact, PC-based arcade hardware has become an industry-wide standard; according to the System 16 Arcade Museum the last console to be used for arcade basis was Sony PlayStation 3. As the cost and options benefits of commercial-off-the-shelf components make every arcade system a gaming PC with unique (sometimes not-so-unique) connections ends the long era of proprietary systems, greater commonality of standards may make things less interesting but there is no argument it makes the games more accessible to the masses which can only be a good thing.