Super Paper Mario, in it's own right, is a good game, but not when compared to it predesesor, it's not.
1- It got rid of the PERFECT battle syestem that started in Paper Mario and perfected in Paper Mario: TTYD, and went to a combat system compariable to Super Mario Bros (you jump on the enmies head/ weak spot)
2- Difficulty. It's simply too easy. Especsialy the Pit of 100 Trails.
But now, I'll try to review this game as if it were a game alone in it's franchise.
STORY: It's very good. The story rarly gets confusing. Also, for a change, THE GAME ISN'T ABOUT SAVING PRINCESS PEACH!!!!! Amazing, I know. I would give a more detailed discription of the story, but I haven't played the game in a couple years and I no longer have a copy of the game to play.
COMBAT: Just like in Super Mario Bros, the combat takes place by jumping on the target's head. Each target has a certain amount of life and it will drop by a specif amount each time you deal damage to it. The Combat systems only flaw I beleive is the fact that this causes the game to become easy. Also if I remember correctly, when you level up, you grow huge and can quite litteraly run right threw anything which makes the game even easier. You can also use multiple other characters as well such as bowser and peach.
PARTNER SYSTEM: I don't remember much about it. Though I do remember that I didn't like it that much.
GRAPHICS: Just like the other two paper mario games, the graphics are quite literally paper. The only difference between the graphics of this game and the graphics of Paper Mario: TTYD is different art styles.