My top favorite Game Genres would have to be in this order; FPS, RPG, Action/Adventure/Platformer, RTS. I usually despise most puzzle games, but there are a few exceptions. (Portal being one of them.)
I'm also starting to like Indie games, because of their cool uniqueness.
My top favorite games, in no real order would have to be; Halo 3, Halo PC, Garry's Mod, Borderlands, Super Mario Sunshine, Paper Mario: The Thousand Year Door, Kingdom Hearts 2, Castle Crashers, Pokemon Blue Version, Spyro: Year of the Dragon, Mario Kart Double Dash, Super Smash Bros. Melee, Age of Empires II.