Cube: Mario Party 5 (4 sucked balls) if you have 4 people
SSB:M, again 4 people is great
MK : DD, try playing 4 people there too

N64: Mario Kart 64, i'm sorry, 4 player battle was the coolest shit ever
Goldeneye with 4 people, too damn fun
Cross-Platform: 007 Nightfire, even with 2 its fun, just put 6 bots in maxed out at the hardest setting
Monopoly Party, you can play 4 people with just one controller, and don't play party mode its gay, play normal monopoly, its just the same but it has ZSNES like save state

PC: Halo PC, 16 people, Pixel Shader 2 goodies, and a fuel rod gun, need i say more
UT2k4: Played it a bit, its ok
JKII: great with alot of people, and no mods and gay shit
Far Cry: have you played it with 32 people, its fun, the machette owns all
wow, i just realized i like everygame i haven't sold