Atari
While Midway handled Pitfall and Gauntlet, Atari was tasked with creating new IPs or creating licensed games.
Microware scored a major victory early on in 2001 when they gained the Tom Clancy video game license.
Atari Montreal was created from talent scalping of Ubisoft as the company generally declined, especially after Ancel's departure from Ubisoft to join Atari France.
Tom Clancy games would be released near annually from the studio including starting with Splinter Cell and Patriot's which released respectively in 03 and 04.
Due to the state of Atari when Microware bought them, they were in dire need of new blood and new studios, fortunately Midway could handle many of Atari's IPs as they already had been, but Ubisoft's decline was Microware's gift.
Atari Scotland
Another major studio of Atari was Atari Scotland, led by RollerCoaster Tycoon and Transport Tycoon creator Chris Sawyer. This was one of Microware's only studios to make games for both the consoles and for the Windows OS as their games needed mouse and controller support.
The Xbox Tycoon Pack would Include Transport Tycoon Ultimate and RollerCoaster Tycoon Gold and was one of the first games on the system to use a keyboard and mouse.
Rollercoaster Tycoon 2 and Transport Tycoon released after the launch of Xbox Live and allowed DLC's and custom rides and attractions, scenarios to be shared over the service.
Due to the entangled state of affairs between Atari and Infogrames Interactive, Microware also purchased Infogrames Interactive for two reasons, to be able to fully control Atari and to have access to the wide variety of IPs that they had assembled over the previous few years.
Gremlin Graphics: One of the studios that became part of Atari, mainly created Atari Golf for both the Xbox and Chihiro and more importantly rebooted Dark Fusion, the 1988 platformer into a metroidvania crossed with a shoot em up platformer.
Dark Fusion: New Millennium released in 2004 to good sales matching expectations set by Microware and was received well by the gaming press.
Ocean Software (Now Atari England) was mainly responsible for the licensed Hasbro games that came from the Infogrames buy out, but did occasionally make their own game such as Operation Reich Fall, a game similar to Operation Wolf, with full lightgun support and online leader boards.
The game released on both Chihiro and the Xbox.
Microware incidentally purchased Firaxis in the convoluted deal, but Microware decided it was better to have them be independent of Atari like Bungie, Blue Fang and Ensemble Studios, but they will be covered at a a later time.
Atari France
Due to Ubisoft's flailing finances, Rayman was sold to Microware in 2004 and Rayman 3 would release on the Xbox in 2005 and Beyond Good and Evil released in 2003 led by Ancel.
Other Atari Studio's
Legend Entertainment:
Was re tasked with making more adventure and TPS games such as Unreal 2 which released in 2004 on the Xbox and the studios earlier game the Wheel of Time was ported to the Xbox and a sequel was released in 2005.
Both games beat expectations and cemented one of the notions of the Xbox as for better of worse the SBox for strategy, simulation and shooting.
Humongous Entertainment was tasked with making children games and mainly educational ones on PC/ Xbox as well as some family games.
Atari Reflections: This studio was working on an ambitious GTA clone focused on a Orwellian future as well as several other prototypes which would turn the studio into a cash cow for Microware.
The game released in 2004 to rave reviews under the title 1984: Watch Dogs a game focused on hacking and fighting a corrupt government in an open world set in Chicago. The game would go on to be a best seller on the Xbox breaking 1 million season in its holiday season.