i played ultimate alliance with 3 other guys, did not enjoy it at all. it's hack and slash, and tons of it, so i could see beating it once and then boxing it up and saying farewell
i don't recommend blitz: the league, either, unless you loves blitz before. try the demo
lost planet is pretty damn cool. gameplay somewhat like gears of war (humans with machine guns vs. alien bug monsters that come out of holes in the ground), has mechanized combat, much of the game played in snow and wind conditions, but i hear the multi is awful
if you like hockey, get NHL 2K7, do NOT get NHL 07
madden 07 is as good as can be expected considerin past quality, but some things like coach mode are absent. cool to play a career in a specific position though, like running back, or wide receiver, or quarterback is very fun (you play form that position's viewpoint with specific controls), standard modes. good football
aside form that i recommend gears of war (duh), fight night round 3 is ok, rainbow 6 vegas if you like first person shooters on consoles (good multiplayer), saints row for a hi-def GTA clone, test drive if you like racing games (it's a massively multiplayer racing game set in hawaii, if that sounds fun get it)
and if you are comfortable with your sexuality and like games such as the sims, animal crossing - viva pinata is colorful goodtimes.