I can't understand how the game's level design could ever be called 'fantastic'. Rayman has fantastic level design. Mario U has the same sidescrolling, platforming we've seen for years. There's nothing fantastic about it. It's standard fare, you know exactly where the hidden parts are, and the actual visuals are 99% forgettable. The haunted swampland, a much talked about level, is literally just jumping from pipe to pipe. Oh and some of them fall down a bit when Mario stands on them.
Because Mario U is Nintendo's flagship IP, and their primary launch game, the ideal opportunity to demonstrate the abilities of their first HD console, and gamepad integration. It was a lazy, rehashed, unoriginal clone of the other three games, just slightly improved.