theres not many with split scrrens but try mario party 8, some other multiplayer games u should definitely try are Super smash bros brawl, and mario strikers charged, if u like football get madden 09
It's a completely different kind of game and may not appeal to you but at least take a look at Maboshi's Arcade (WiiWare). Up to three people can play at the same time and their games interact with each other. I think it is crazy fun. It has received great reviews. But it never made it into the top-20 games in the Wii Shop so apparently it hasn't sold well. Sigh.
Here's the MetaCritic link if you want to find some reviews: