I dont think its just one. And the previous posts have got it right
My opinion: 2000’s
-GTA3/San Andreas
-Half Life 2
-World of Warcraft (MMO’s to the next level)
-Halo (Next level what Golden Eye did for console shooters in the 90’s)
-RE4 ( 3rd person over the shoulder camera angle )
-Gears ( 3rd person shooters)
-Dark Souls (I know Demons Souls started it but Dark Souls was a commercial hit that everyone knows)
-Skyrim
-Cod modern Warfare
-Uncharted 2 ( Story driven action games, cinematic set pieces )
-Super Meat Boy, Limbo for that indie like revolution
-Minecraft (Dec 2010 Beta release ) but this could be classed as 2010’s.
Before the 90’s- 2000’s is also interesting
Heres just some
-Tetris ( Yes it was released in 1989 but gonna include it)
-Sonic ( Gaming rivalry Mario vs Sonic )
-Doom ( We all know why )
-Street Fighter 2 (Took games and fighters to a new level)
-Final Fantasy 7 (Put JRPG’s and RPG’s on the commercial map)
-Resident Evil/Silent Hill - Survival Horror Genre is born
-Gran Turismo ( Racers became more popular than Ever
-Mario 64 - 3D Platformers
-Zelda OOT - 3D Adventure games
-MGS - Took Story telling in games to a new level
-Golden Eye ( Took 1st person shooters/multiplayer games up a level for Consoles )
-Quake 3? Unreal Tournament? Counter Strike - Competitive online shooter
Others: Half Life, Diablo, Civilisation, Sim City, Command and Conquer. Star/WarCraft. Ultima Online. Mario Kart. Sims