I would love to see a new Luigi's Mansion on the Wii, or even a NPC Luigi's Mansion (because I never owned the GCN version)
Currently dreaming of: DKC4 or Sonic the Hedgehog 4 (classic 2D platformers) for WiiWare, Smash Bros. for DSi, New Super Mario World for DSi, a Wii remake or true sequel of Final Fantasy Tactics.
One down, hopefully more awesomeness to come.