Kirby's Epic Yarn is probably one of the most enjoyable Wii games I've played in ages. Wonderful graphics, the controls handle pretty well in my opinion, and the levels are pretty straightforward without being too easy-peasy. It's a good game to play when you need cheering up; I swear, me and my roomate were squeeing over some new tidbit every five minutes. Maybe less.
Also seconding the LEGO games, especially LEGO Batman. That's one of my favorites.