360 - Mass Effect - I imagine Mass Effect 2 will beat it.
DS - Legend of Zelda: Phantom Hourglass - Sprit Tracks may beat it, also I haven't played Scribblenauts or Chinatown wars.
Wii - Uhh. . . I guess Wii sports, to be honest I haven't finished a Wii game yet. I think I'll really like Metroid: Other M a lot though.
PS3 - Uncharted - To be overcome by. . . Uncharted 2!
PSP - I would have to say Resistance: Retribution. It will stay as top, I sold the PSP.