GB, you are going to absolutely LOVE the Wii. The Wii Fit rocks too. There are tons of different games and things on there and you can use it as a "personal trainer" too if you like. There are strength, balance, aerobic and yoga things on the fit. You can also get other games that utilize the Fit board.
The games that come with the Wii are a blast too. The baseball, bowling, tennis and golf are awesome, but I completely suck at the boxing. Madeleine (who's birthday is also tomorrow) creams me every time I try it out.
If you are looking for serious party fun look into the Guitar Hero world tour for Wii and get the drums, bass, guitar and microphone. Its a party all on its own. A bit $$$ though.