If you thought NSMBU was an okay game or more, you HAVE to buy Rayman Legends. The reason i bought a Wii U in the first place, and I hadn't really played any Rayman game before. I played much of Origins with a friend just before Legends launched, and it didn't disappoint. I see some people here played Origins but not Legends, and I'll say one thing: Legends is much, much better than Origins. A whole lot of levels from Origins are included as well, as bonus worlds. Legends actually feels like a new game, unlike what I felt from NSMBU (it didn't help that the subpar NSMB2 had launched just a few months earlier...)
To the OP: Buy Rayman Legends as soon as you can. It's definitely one of the best games of 2013.