Fuzion Frenzy (for the original xbox) - still the best "party game of the xbox family. The 2nd one was absolutely HORRIBLE!
Small Arms (Smash Brothers Style game)
The Bigs (A baseball game that's arcade style - fast paced and over the top - 2 players per team)
Aegis Wing (FREE arcade game that's pretty fun)
That's it for four player games that I've played that aren't FPS style.
If you are okay with FPS style - we had fun with COD2 and Perfect Dark Zero, with four players on a projector screen.
FF2 is fun and all but it just pisses me off that half the game is 'locked' and you have to do all this crap just to unlock them.. so annoying, i paid for the dumb game why do they have to make it so difficult to access all the content.. not even cheats that i can find.. meh