I know you probably don't want to hear it, but if you want party games, right now the Wii is what you're looking for.
Comes with Wii Sports and it's ridiculous how addictive it is. Also out for it right now, Rayman Raving Rabbids, Elebits, Wario Ware: Smooth Moves, Super Monkey Ball ... all straight up party games. Wii Play is supposed to be out later this month I think (and it comes with an extra controller), with more party games. Also in the near future is Super Smash Bros: Brawl, Mario Kart, Mario Party, Super Strikers (soccer party game), and more on the way.
Other good multiplayer games (not necessarily "party" games), Excite Truck (2 player only though), Rampage, Dragon Ball Z, and there's other 3rd party games (also on other systems) like Need for Speed: Carbon. Upcoming games like Bleach are in development.
Then the single player games like Zelda: Twilight Princess, Red Steel, and Call of Duty 3 (if you don't already have it for 360 or PS3), and up-coming games like Metroid Prime 3: Corruption (may be online multiplayer), The Godfather, Super Mario Galaxy (if you like the SMB games), Project: Heroes (Killer 7 sequel, and my be multiplayer)