There are 19 million Kinects in the wild and very few good games to play on them. I think most people will say that Dance Central is the best (partially because it seems to work more than 75 per cent of the time). What's second best?
It could be the upcoming Fable: The Journey.
I grabbed some time to play the game on the final day of E3 last week. Then I filmed one of the game's developers play a boss battle. The video will explain most of what's good about the game: the simple but effective gesture-based magic-casting, the minimal need to control body movement (none of that silly lean-forward-to-move-forward from Kinect Star Wars).
Keep an open mind and give it a look.
One caveat: Early on, while I was shooting this, I stepped in a hole on the Fable: The Journey E3 stage. That's why, briefly, you can't see the game well. I didn't have time to re-shoot, so please just bear with it. And, no, I wasn't injured. Thanks for asking.