Here's my list of DOs and DON'Ts regarding purchasing wii titles. I own or have played all of these titles.
DO get Sonic and the Secret Rings, because its a fun platformer with snazzy visuals.
DON'T get Far Cry Vengeance because the graphics look like they belong on an N64.
DO get COD3 because, while flawed, it is still a good shooter.
DON'T get WarioWare because it is really boring and unless you like making an ass out of yourself in front of friends, it's no good for multiplayer.
DO get Super Monkey Ball: Banana Blitz, because its a really fun game and works PERFECTLY with the wii remote, and no one seems to mention it anymore.
DO rent Elebits, because though it's fun, it gets old fast and the graphics will start to bother you after a while (the slowdown only makes it worse).