Golden Axe (you have to download it) Its old but VERY fun for 2 people to play. Dragon Ball Z: Budokai Tenkaichi 2 is a good fighting muiltplayer. Excite Truck has 2 player racing. Metal Slug Anthology, and Call of Duty 3.
But I think Wii sports is the best for multiplayer right now. It has 5 games to play and also if you still just have one Wii remote you csn play Bowling and Golf.