FPS: Call of Duty 4, Doom 2, Quake 3 (more for engine than game)
Strategy: Homeworld, Supreme Commander, Star Wars Rebellion
RPG: Star Wars Knights of the Old Republic, Diablo 2, Elder Scrolls 3: Morrowind
MMO: World of Warcraft, Hellgate London, Team Fortress 2
Sandbox: Simcity 4, Sins of a Solar Empire, Pharoah
Other: Star Wars: X-Wing vs Tie Fighter, Mechwarrior 4, Halo
Edited to add the greatest RTS ever made.