Mario has never had a more artistically detailed game in his entire career and the story is new and improved.
When I think of Mario, I think about his cheating girlfriend who seems to get 'kidnapped' by Bowser every other year. What this game surprised me with was the fact that the plot wasn't centered around only you saving Princess Peach from Bowser's clutches. In this game you save Princess Peach from Bowser in the first fight of the game, then later in the game from some bearded pirate. But, along the way Mario has to find the seven magic stars to repair the star bridge for a magic doll that shoots bullets from his body, help a guy that thinks hes a frog figure out his past, kill hundreds of insane creatures, and destroy a ruler known as Smithy. So this is a HUGE upgrade for a Mario game's plot compared to the often used formula of having A beat up B to rescue C. There's also a small bit of humor and some interesting dialogue that actually adds a lot of depth to the characters in this game which are visually interesting and seem to have their own very unique but believable personalities. Most Mario games have characters with little to no story or depth to them and are only meant to add to the game-play and have nothing to do with the game's story. In this game that problem has been swept clean and replaced with an actually decent cast of characters who make more sense in terms of how they respond to certain situations and what their skills and talents are.
Game-play and Art design
I normally don't like RPG elements employed in a game that are designed to lengthen game-play by having you kill the same enemy like a billion times to level-up but Super Mario RPG makes this work correctly. They did indeed make it so you had to kill the same enemy a few times to level up but to balance the manipulation of that out Nintendo made everything look artistically interesting. Plus, to make things a bit more challenging you had to not only choose which attack you had to use since this is a turn-based RPG but also correctly time when you hit the attack button for more damage.
Review Summary
Sadly, Nintendo owns few or no other games in their library of games that has a well crafted story like Super Mario RPG. I'd even go as far to say that Super Mario RPG has the best looking art-design (not graphics) implemented in a Mario game ever. However, the game-play has the flaw of being repetitive just like all other turn-based RPGs seem to have but this is the only major flaw I can find within this game. Other than this, Nintendo managed to create another gem out of thin air.