What kind of game would that be though? Assume, for the sake of argument, that the Kinect 2 works nearly flawlessly within its proven abilities. Heck, I'm not even sure where the limitations are, but assume something near the top of what you have seen so far in tech demos. I am fairly stumped for gestures that I would even find useful in an augmentation fashion much less a game built around a gesture interface. Maybe a virtual touchscreen? Wouldn't voice be faster and likely more reliable? I have yet to even read about a compelling use of the camera system for a game.
One of the biggest issues for the kinect is world traversal. Without a controller or a specific gesture that doesn't tire someone out moving through a world will almost always mean on rails. Movements with a controller only need a controller that senses motion.
My first thoughts on the subject was of course Force powers in Star Wars but then unless it's on rails .... then I thought of a Wizard/Shaman sim where you speak incantations and gesture in specific ways in synchrony ( ps camera could do it as well). Add the pulse monitoring ( to mimic the magical trance ) and you would have quite a deep sim that can't be done anywhere else. Again you would be on rails or just find a neutral hand or head position to dictate direction.
Besides dance and exercise I don't know what the kinect could do specific to it at this point.