I don't think any game would ever make me buy a Wii. I know lots of friends who has a Wii, and I've played some games with them, but I just don't... "get it". I don't find the console as much fun as all the hype made me assume it was, but I guess that it might be because there are no achievements
A little off-topic: I have a PS3, too, but the Trophy system isn't really as catchy as the achievements either.