Wii: Super Smash Bros. Brawl
GameCube (on my wii): Super Smash Bros. Melee
PS2: Guitar Hero 2, It has a better music selection *cough*Jordan*cough* than GH3, I expected a lot more out of GH3.
PC: Half-Life 2 and Episodes 1 and 2
Elder Scrolls IV: Oblivion, I am now getting into the modding community of ES4, since I have completed 95% of the quests in it.
And a little bit of JK:JO