The question should consider which one is better for its purpose.
The answer is obviously the kinnect, the eye is just an inferior device. Its not about which one is least offensive to you or whatever, Im sure dance games don't appeal to most hardcore gamers but that's not the point. The kinnect does those games the best by default and such games are a case where the motion sensor as a controller is fundamentally a superior input device vs a game controller.
Plus voice controls do have potential in games, and the kinnect has a fancy noise canceling mic system.