Action/Adventure: Twilight Princess (not far enough into Skyward Sword to say yet)
Runners up: Assassin's Creed 1 and 2
Racing: Need for Speed: Hot Pursuit
Runners Up: Mario Kart DS, Forza 3
RPG: Skyrim
First Person Shooter: Halo Reach
Runners Up: Call of Duty: Modern Warfare, Halo 3, Borderlands
Third Person Shooter: Mass Effect 2 (or would that go in RPG or Action Adventure)
Fighting: Super Smash Bros. Brawl
Platformer: Super Mario Galaxy
Runners Up: Little Big Planet
Sports: NHL 12
MMO: World of Warcraft
Puzzle: Portal 2
Minecraft: Minecraft (one of the best games this generation but kind of category-less)