Not only is SPM a HILARIOUS game, but it's also very innovative in that a game like this has never before been done.
However, while what I described above sounds like a platformer, the game also feels very much like an RPG. For example, as Mario defeats enemies, he games experience (referred to as your Score in the game), and he can level up, increasing either his Max HP or his Attack Power. Furthermore, the game is VERY text heavy. You'll almost be reading as much as you're actually playing in some parts. The storyline is nicely done, and the dialogue is witty and hilarious. I never thought moustache jokes could be so funny! Overall, SPM has awesome and innovative gameplay, combined with hilarious dialogue.
Graphics and Sound: The graphics in the game are amazing. Sure, the game could probably be done on the GCN or even the N64, but the style is just so innovative that I can't help loving it. Everything is bright and colourful, and is pretty much what you would expect from the Paper Mario series. The sound is excellent as well, and the music and sound effects are all nicely done.
Value: By platformer standards, SPM is a long game, but by Role-Playing standards, its length is under average. Regardless, I feel like it lasted the perfect amount of time. When I beat the game, I was at 25 hours played. Plus, the game lets you continue playing even after you've already beaten it, and there are plenty of things to do, such as the Pit of 100 Trials (there are 2 of them in this game as well!). So overall, while it's no Zelda in terms of length, the games still pretty meaty and should last you a while.
Tilt: Overall, Super Paper Mario is an amazing game. I never imagined that it would be THIS good. Not only will it keep you laughing out loud the whole way through, but it's got some great gameplay as well. The storyline is entertaining as well, and has a few twists throughout that are pretty cool, and everything looks and sounds top knotch. It'll also last you a pretty long time. In the end, I highly recommend this game to all Wii owners. It's an incredible game that you should not miss out on.