I'd have to say either Animal Crossing, Mario Kart DS, NSMB or Phantom Hourglass.

I'd love to see a very realistic Zelda game (though art wise it doesnt really bother me). I want to see bruises and cuts on Link's body and his clothes torn when he has low health. I want to see all sorts of weather all around Hyrule, maybe a few natural disasters sprinkled in as well (hurricanes and tornadoes etc). Enemies that are truly challenging, and bosses that need real strategy behind them. The land of Hyrule that has a lot of hills and mountains that enable you to see a breathtaking view of the kingdom. Numerous side-quests. Also, even though I know Nintendo will not include it, but I want to see blood. It would be much more satisfying to actually see enemies' bodies being sliced and diced with blood spilling everywhere. But most of all, I would like to see visuals that really pushes the Wii to its limits, and fully orchestrarted music.

I better lie down after typing that.

The Conduit for me. From what I've seen it's got amazing graphics and it's got Wi-Fi multiplayer.