Remember when the first 2 Paper Mario games were RPGs? Super Paper Mario makes the battle system a lot simpler this time, but despite a better battle system, this game isn't as good as the previous installments.
This time, not only is Mario playable, but once again, Peach and Bowser, and eventually, Luigi, are playable, and each of them have special powers to progress through the game. Mario can flip into 3-D, Peach can use her parasol to float, Bowser has his fire breath, and Luigi can reach high places.
This game is basically the Paper Mario equivalent of MOTHER 3, but with emphasis on terror rather than somberness, even though there are tragic back-stories for a few new characters. Speaking of which, some of these new characters that travel with you are Pixls. Aside from Tippi, the Pixls have no personality whatsoever and aren't memorable like the allies from the previous games.
If you liked the first 2 Paper Mario games, then... do whatever you want.
My rating: 8/10