Zumba Fitness is actually a great exercise game on all the platforms. I'd say the Kinect version is definitely the best one. The reason it got bad reviews is because people were expecting Dance Central. Zumba is more like Just Dance where you just move and scoring is not important. If you want precise scoring and leaderboards, Zumba Fitness is not for you. If you want to dance to top 40 pop songs, Zumba Fitness is not for you. For that stuff, Dance Central is better. Dance Central is more of a game than Zumba Fitness.
the big problem with the Zumba game is the tutorials. they were touting the tutorials as if they were like DC. but the tutorials are broken and overly hard. don't even use the tutorials. just jump into the dance classes and do it. If you want to learn the steps, skip the tutorials and do the individual dances rather than the classes (which are medleys). Zumba is more about doing it. You'll get better over time and the steps are repetitive enough for someone to learn it.
If you want aerobic dancing, Latin-style, then Zumba is great. The Xbox version even has 8-player online multiplayer and you can definitely find a lot of people online to dance with. Heck, quite a few times I started a dance class and lots of people jumped in mid-dance. You can chat with people while you're dancing too. It's like being at the gym class but you don't have to see them.
The Xbox version has local 2 player simultaneous or 4 player teams (2 versus 2).
the great thing is the dancing is geared toward exercise. the problem with Dance Central 1 (which they addressed with DC2) is that you can't set continuous playlists. when you're exercising, you can't have 30 sec-1 minute breaks in your exercising (in DC1, you have to scroll through a song list after each song finishes). you want continuous motion. in Zumba, you can set 1 hour classes, 20 minute classes, etc. it still has breaks (it'll tell you every once in awhile to get water) but the breaks make sense from an exercise perspective.
but Zumba requires good knees. this game is very hard on them. there's lots of spin moves and fast sudden changes moves. it's the same advice you give to heavy set people who want to jog for exercise. you need to work off some of the weight before you go hardcore Zumba or you need to stick to the easier lessons.
if you are into scoring and are comparing the different versions of Zumba Fitness, they're all the same in terms of poor score tracking. with the Wii and Move versions, you wear a belt that holds the controller. or you can just shake the controller wildly and get "perfect" scoring. all 3 versions of the game all pretty much have the same interface and same graphics. the only difference is the Kinect version lets you see a silhouette of yourself in the background. and when you play online multiplayer, you can see your friends' silhouettes in the background (only the silhouette!).
Zumba is not about leaderboards and scoring. Regardless of what platform you play on, you'll have a good time in Zumba if you fit in that demographic.
on the Kinect: http://www.youtube.com/watch?v=yIIdn-_zALg&feature=channel_video_title
on the PS3: http://www.youtube.com/watch?v=1JRG0GbB5oQ&feature=player_embedded
here it is on Wii: http://www.youtube.com/watch?v=NV3_Qg2dYZA