I dunno man, I personally just got the game a few days ago and I'm loving it.
I'm two bosses into it so far..and I keep finding myself drawn back to the wii for some more..
(come on just one more star..then we can go back to work..i mean it this time...last one..>_>) <- that's kinda the inner monologue I've had for the past 12 hours.
I think this game is infinitely better than mario sunshine and IMHO better than Mario 64 (readies flame shield), The art design is beautiful, the physics are fun to explore, the game is great..once again this is my opinion.
I say give it more time, get a bit further and see if you still regret buying it.