Nintendo made an interesting experiment with Super Princess Peach. The tables turn as it's Peach's turn to save Mario.
Princess Peach Toadstool of the mushroom kingdom is usually stereotyped as the classic ''Lady in Distress'' whom has to be saved by Mario.
The tables turn as it is Peach's turn to save Mario and Luigi from Bowser's evil claws. The game is a very fair platform game and it will not be considered as a Super Mario Bros. game, because the Spin-off is just too diferent from the others (Although Yoshi's Island is considered a Super Mario Bros. game even if it was totally different from the other Mario games).
The game has a very sunny fresh style, it takes place in an Island that's close to the Mushroom Kingdom, the island is called Vibe Island.
The bad thing about the game is the lack of challenge, it is way too easy for any average platform gamer, Your final encounter with Bowser may be the only hard part and that is much to say because if you die you can just try again untill you get it.
Overall: Super Princess Peach is a great spin-off for the Mario series and it is so worth checking out.