There's nothing more laughable than N-tards towing the "third party games sell on the Wii" line. In order to justify this position they compare PS3 software sales - you know, the system barely anyone has. They never want to talk about the Xbox 360, the system that's leading software sales by leaps.
Wii gamers want minigames, rehashes, and superior ports - preferably from Nintendo. Orginally third parties tried to re-create that magic but failed. A few have tried more elaborate games in Japan, which bomb too. At the end of the day the people who make the Wii a success are still the snotty nosed Ntards who think Geist is a better shooter than Halo. Granted a large portion of grandmas now make up the userbase, but I'm more than willing to bet they've bought around 1 game since the Wii's launch: Wii Play. Nintendo isn't expanding the market, they're convincing non gamers to buy the new fad, play with it a few weeks, then forget about until Christmas party season.
If you want to make a Wii game that doesn't utterly bomb, your best chance is to make a kiddie game a parent might mistake for Mario or Pokemans