Crash of the titans, is very good solo player, and it has a jump in/out co-op mode, which is where another person just hops in and plays along as another crash, very fun. 1-2 players
sonic and the secret rings, i liked the game some did,t but the mini games selection on it is very fun for multiplayer 1-4 players
marvel ultimate alliance has same type of multiplayer as crash, jump in jumps out but is for 1-4 players, fun, but not as good as crash
excite truck 1-2 players, ok multiplayer,
red steel 1-4 player, i really liked, but is most fun with 3 or 4 players, as the four players, opens a really fun mission mode multiplayer,
wario ware smooth moves, 1-12 players, (only uses one remote shared between 12 people). personally this game was fun for 5 mins then crap even shite from there after, but the multiplayer is ok and lasts a lot longer, but can still be very crap.
soem others dont remember.
but seriously next month is the month for great multiplayer,
medal of honur heroes 2.
battallion wars 2 (i think thats november)
mario galaxy (single player seems pointless though lol