Out of this list, I've played:
Batman: Arkham Asylum
Halo 3: ODST
Borderlands
Braid
CoD: Modern Warfare 2
Left 4 Dead 2
Minecraft
New Super Mario Bros Wii
Plants vs. Zombies
For me, it's not even that close, Left 4 Dead 2 takes the cake. The amount of content in that game is astounding. The weapons are great fun to use. The map design is some of the best in any FPS (Dark Carnival is one of my favourite maps of all time). The versus mode is too much fun. It's definitely best on the PC though.
Braid for best indie game, loved the art style, game mechanics, and storyline (that twist was amazing).
CoD: MW 2 was great for multiplayer. Nothing groundbreaking, just a lot of fun.
Plants vs. Zombies is my favourite mobile game.
Batman was the best single player game out of my list.