They dropped the price, and you might be able to get a used one.
I have the launch title Fitness Evolved, but haven't been able to play it much due to an injury. I actually like the workouts on the Biggest Loser better - cause I could do them and it had more variety. But I hear the Fitness Evolved 2012 one is improved and I am not sure if there is a 2013 Fitness Evolved.
I find a couple of the games in Adventures sweat worthy.
I get a good sweat up playing Powerup Heroes. But I seem to be the only one, and you can get that very inexpensively. It is repetitive, but really fun once in a while.
And try the demos of Fable the Journey and Kinect Star Wars.
And since you already have a Wii I really like the sword fighting game in Sports Resort.
While Dance Central 3 got a 10, Kinect Nike got a 4 out of 10 which was rather dissapointing.