Well, I bought a Wii. I told my son it was mine but if he behaves, I'll let him play with it. That worked for a while. ;-)
I got legend of zelda: twilight princess, a spongebob action game, a cart racing game and it comes with a sports game. The sports game is my favorite. Bowling is amazing and I like tennis quite a bit. Spongebob was winning with my son until the wife went to blockbuster and rented lego star wars. My son is totally addicted now. He may have withdrawels when it goes back on tuesday.
It is a neat game. It has its hard points but over all is pretty easy. My son has become a master pod racer. I was watching him play and was getting dizzy but he didn't have any problems. He even laid down and played it prostrate.
The only downside is that now I don't have a TV. If he's not Wii'ing, the wife is DVRing.
C'est la vie. If you are able to get a Wii, go for it. It is worth the money. The wife wants Wii Fit when it becomes available. She'll probably get more exercise wresting the Wii away from my son. ;-)