Microsoft Buys Bethesda: EVERY Studio Xbox Now Owns
2. Id Software
Notable Games: Doom series, Quake series, Wolfenstein series (1992 - 2006)
Id Software is not so much an FPS studio, but rather THE FPS studio. Period.
Founded in 1991 with a superstar cast of developers, they singlehandedly invented the FPS shooter with Wolfenstein 3D, then reinvented the genre with Doom (1993) before inventing the online shooter with Quake - all in the span of three years.
Supporting Quake become the studio's main focus and slowed its momentum. Also, id's big comeback, Doom 3 in 2004, was a slick effort but divided fans, as it prioritized survival horror over the original's arcade-y action. Then, a lengthy development cycle for Rage - and also Doom 4 - left them in a vulnerable position.
Fortunately ZeniMax made them an offer they couldn't refuse in 2009. Sure, the Rage franchise never took off, but the rebooted Doom series is arguably the best the series has ever been - a fantastic blend of frenetic retro action with slickly modernized mechanics.
For Microsoft to be the future owners of the inventors of the FPS genre is dumbfounding stuff, but also a true match made in heaven.