XBOX 360 and Kinect is a hoot. My sister has one and its a riot to play Dance Central on. My little niece who is 3 absolutely loves the Kinect and its games so it is a good excuse for my sister and brother in law to buy games hehe. The Wii is cheaper, but it requires you to hold onto the remotes. The PS3 move also requires you to hold onto stuff in order to play, but a PS3 would double a blue ray player.
Guess it comes down to personal preference..
I chose an Xbox since most everyone I know has one and I prefer the games that are Xbox exclusives. I wish Microsoft had a blue ray drive on the Xbox, but I rarely watch movies anyways, so it wasn't a deal breaker for me. Also, I plan to buy a Kinect in the near future, so the Xbox was a no brainer for me...
Ohhhh yeah, Forza 4 (xbox exlcusive game) has a TON of muscle cars that you can race if you're into racing games. '68 Dodge dart gts, 71 cuda, etc