The original is the best.
Story: All RPGs need a story for you to role-play, don't they? Peach is sitting at her castle without Mario nearby (You know where this is going) to welcome the ambassador from the Mushroom Kingdom's previously unmentioned neighbor: The Bean Bean Kingdom. The "Goodwill" ambassador walks in and offers Peach a gift, a gift that explodes a cloud of gas into her face and causes the princess to fall face first on the floor. The ambassador laughs and transforms into a diabolical creature and flies off with its apprentice, leaving Peach unconscious on the floor and the many Toads in a panic. Only one Toad has the sense to do anything, this being everyone's favorite Toad: Toad himself. He rushes off... to find Mario. Hey, don't expect too much of him, he's not human after all. He reaches Mario's house and sees Luigi hanging up Mario's clothes on the line, he asks where Mario is and rushes into the house upon hearing that he's in there. You learn how to move people around here as you use Toad to explore Mario's house. Enjoy it since the rest of the game is spent playing as Mario and Luigi. Toad then walks into the bathroom (A bathroom in the Mushroom Kingdom? Mario finally can do something with the plumbing) and into the shower, where you lose sight of him. He hears Mario humming, and then surprises Mario in the shower, which causes poor Toad to get incredibly embarrassed and rush out, directly into a dresser. Mario comes out wearing a towel, and the semi-conscious Toad manages to say "Th-th-the p-p-princess." Mario panics and rushes outside, jumping onto the clothesline and magically getting dressed in a flash of dust and runs off with Luigi tangled up in the clothesline. Thus starts another exciting adventure in the Mushroom Kingdom. And no, Luigi isn't tied to Mario the entire game. I'd tell you more, but the plot changes about five times (Including a change where you learn that you did half the game for nothing, joke's on you).
Gameplay: An RPG in a loose sense, since it's not like many others out there. You control a party of two, you interact with the environment as much as battle, you gain powers throughout the game, and can dodge attacks with timed button presses. Sure it's been done before, but not quite as good as the best. And this IS the best. You control Mario or Luigi by themselves with the D-Pad to move, the A-button to use various actions (Jump, hammer, and elemental move) and the R-button to change between the three. But the main portion of the game involves moving both bros. at the same time, you control one and the other follows directly behind, also controlled by you. The D-Pad moves your bros, the A button controls the commands of the bro. in back, the B button controls the commands of the bro. in back, R switches the front bro's command, L switches the back bro's command, Select pauses and opens your suitcase, and Start switches the front and back bros. Simple, but it gets more complicated as you gain more powers and learn new techniques, eventually you have ten different commands to work with and you'll be pressing the L and R buttons almost as much as A and B. You journey all around the Bean Bean Kingdom in an effort to save Princess Peach from four or five various predicaments, as well as save the Bean Bean Kingdom (Which is friendlier then first appearances) from the witch Cackletta and her assistant, Fawful the traitor. Outside of battles you wander around the world, solve various puzzles that crop up, and start fights with the local unfriendly inhabitants. Inside of battle Mario is controlled by A and Luigi by B, regardless of which order they're in. You attack the enemies with jumps, hammering, or elemental attacks (Once unlocked), and then dodge their attacks by jumping or whacking them with hammers. Unlike most RPGs you can't just sit there and take damage, you WILL die if you don't try to dodge, which is better then it sounds because you're now in control of when the enemy hits you, rather then a random agility/dodge stat. The faster hero/enemy goes first, but considering you can dodge speed isn't quite as important as in most RPGs. The person to kill the other first wins. If both of your bros. die you can restart from the last save point, or warp to the castle. If you win you gain EXP/coins from the fight, coins are used to purchase items at the shops and EXP is used to gain levels. But you knew that, didn't you? For a level-up you are given a set amount of points to every stat (0-5 points to HP, attack, defense, BP, speed, and stache) and can choose a random stat to give a little extra to. But don't focus too much on one stat; you get higher numbers from alternating stats. HP is your health, attack increases damage given, defense decreases damage taken, BP is special (Bros.) points for special attacks, speed is already explained, and stache is a secret stat. Don't worry, it's explained in-game. After the fight you resume exploring, and continue to explore fight, and solve puzzles until you reach a powerful enemy (Boss) which you have to fight to advance. It's a basic RPG outside of the battles and characters.
Characters: Mario is the noble, valiant hero who isn't quite the main character oddly, as Luigi steals the show. There are several times that you have no choice but to play as one bro. as the other is preoccupied being poisoned, being captured, being trapped in a barrel, and escorting the princess, of which Luigi does one and Mario all four. In the end you play as Luigi more then Mario, Luigi even gets his own exclusive boss to fight. Luigi also steals the comedy with his cowardice, which always causes people to pay more attention to him then they should have to. Peach appears too as the principal character in distress, Bowser plays an ally, an obstacle, and the creepiest Mario character ever at various points in the game, Toad's role is summed up above in story, Yoshi's kind are present, even the Koopalings come back as mini-bosses. Queen Bean, Prince Peasley, and Lady Lima make up the nobility of the Bean Bean Kingdom, Professor Elvin Gadd owns the local coffee shop, and the land is populated primarily by beans.
Bean Bean enemies include Beanies (Beans gone bad, compare to Goombas) to Troopeas (Think Koopas on all fours) to Spikeas and Lakipeas (Spinies and Lakitus) and variations on Snifits. The Bean Bean Kingdom also borrowed some Mario foes, such as Goombas, the various Bros. (Hammer, Boomerang, etc.) from Super Mario Bros. 3 and some new ones, Rexes, Dry Bones, Boos, Magikoopas, and the above mentioned Snifits. Cackletta is the main antagonist, of unknown species (Looks like an asparagus), and has the abilities to hurl lightning, create black holes, and possess people (Creating the creepiest Mario character ever). Fawful is a traitor bean who joined Cackletta's side, and can fly with a vacuum helmet, vacuum things with said helmet, and fire laser bolts with the same helmet. He also has some of the funniest lines in the game, ones that are so overused that they're not funny anymore.
Technical Details: Despite being a 3-D game the graphics are in 2-D, but this never messes up gameplay any, and makes the portions of the game where you move sideways (Not very many, mostly hidden) look realer, but the game still is definitely 3-D. The music is mostly new, with brand new tunes and remixed versions of old ones, and the sound is classic Mario, you've got jump, hammer pound, attacks, defends, element charges, high jump, spin, and a ton more. Okay some are new, but they sound like what they would have been had they been original Mario sound effects. The controls are effective, and while it might take you a little to get used to them it isn't ever very hard, and you can't die outside of battle so there are no severe penalties. Note about the camera: Some (IGN) has complained about the top down camera being a little more front to back view, but I've found no problems with it.
Lasting Value: The game lasted me about 8 hours before I beat it my first time, and then another four for sidequests (Bean collecting, mini-games, a miniature version of the trading game which is merely a couple of items to a couple of people for a couple rewards, etc.). Then I reset it and beat it again. Then I reset it and did a speed run, beating it in six hours. Then I reset it and did it again. And again. And again. And now I have two slots available at all times, one that I reset whenever I want to beat it again and one that has both bros. at level 61 and getting higher. But not everyone will feel the same as me, some people may beat it once and then be done, which is fine by me, but the game won't last that long by that method. For anyone willing to replay it, and the game is good enough that you won't likely get bored, it can have infinite replay value. But remember: You can't skip half the tutorials, so going through them again may be a bit tiring after your third playthrough.
Gameplay: 10/10
Graphics: 10/10
Sounds and Music: 10/10
Fun: 10/10
Replay Value: 8/10
Overall Score: 9.6/10
Pros
Epic story
Different gameplay is done well
Game is fun
People willing to play forever will not get bored
Cons
Control scheme may be a bit confusing at first
Tutorials get old
Luigi is a spotlight hog
Bowletta (Don't ask)