I've played Just Dance 3. I've tried Dance Central 1 & 2. I've played this one and although I feel there is a big limitation of songs on this game - the dancing just feels "right". Rather than copying static cards - this game actually shows you on screen what to do. So you trace the lines with your hands, hit the bubbles, etc. I love this way of dancing - it's easier to follow than static cards. However, these movements won't really teach you any cool dance moves. You might look a bit special but it's fun and to me, that's what's important.
What might bother people is the music selection. There is Club, R&B, Pop & Para Para. None of them are top hits. I think they were just from Konami's music library but in my opinion they are a lot of fun - I would love it if they used top hits you can dance to but the music isn't bad. There also isn't many of them. There's about 20-25 of them. People who are familiar with Japanese Anime & Manga would recognise the kinda genre that is Para Para. If you usually like Anime intros and outros - then I think you would like this genre.
I also think it's a bit too easy. After about a day of playing on it - I could get A on Extreme on some songs whilst eating an ice cream. But it just shows it's a game for everyone - I have only ever got a AA once.
But overall, great game, highly recommend! Unless you're into all that hip hop top hit stuff. If you're in it for top hits then Dance Central/Just Dance is a way to go.