Xbox, Kill.

For anyone raised under a rock, let me just tell you that the Kinect, though masquerading as a "Wii knockoff", is actually quite amazing.

Having spent a little time playing it already, and waiting my turn as I type this, I'd give it a 6/10 as far as "Jesus Christ you need to own this". The games are fun, and the gameplay is unique to this peripheral. Whereas in the Wii you only really had the accelerometer controllers, the Kinect makes full use of your body. You control the actions on the screen based not only on your movements, but also your distance from the device itself.

This is particularly necessary in games like Space Pop, which although it takes some intensely unflattering photos of you, is quite fun.

Another awesome feature of the Kinect is the ability of it to recognize faces. While playing a game such as Kinect Adventures, having to switch places / users is simplified by the camera recognizing the face and body language of the person in front of it, logging you in or out without a single command.

The downside to Kinect's verbal controls is primarily the need to speak extra clearly. It almost completely depends on your ability to enunciate and speak with enough volume that the device understands you. It also responds to a uniquely small list of commands. Saying something like "Play" to play a disc should be sufficient, but because of the Kinect's vocabulary, saying "Play Disc" is necessary. This also means [rather unfortunately], that you can't ask the Xbox to kill, maim, or mutilate your friends, make you a sammich, or bow down to your greatness.

That being said, play with one. Your life will be so much more awesome.