Even to those unfamiliar to RPG games, this is a highly addictive, enjoyable game.
The reviews are right. This game is awesome, even to someone like me who doesn't like RPGs. This game has more than just role-playing elements. This is a perfect blend of exploring, platforming, battling, and socializing. This is a lengthy, satisfying quest with plenty of re-exploration and areas that you can navigate further later in the game thanks to acquired moves.
You can play as Mario and Luigi in a 2D platforming world inside Bowser's body, or as Bowser in a normal 3D isometric world. Often times, you will switch regularly between characters to accomplish goals; eg. In order for Mario to reach a high platform, Bowser must drink water to fill up his stomach. Then Mario can swim up to the platform.
Battles with enemies are exciting. Each enemy has a "tell" and a weakness, and once you discover these, you become very satisfied. There are a variety of normal attacks, special attacks, defenses, and recovery items, and when they are used with correct timing, you can defeat an enemey without taking any damage.
The boss battles are epic. These baddies have an onslaught of attacks, each with a special way to avoid them. They all have a special weakness, and I have not come across a single boss fight that wasn't satisfying. The giant Bowser battles are especially fun.
Graphics, while not PIXAR film quality or anything, are still very stylish and makes full use of the DS's pixels.
Music is decent. There are some catchy tunes, but most of them are simply good.
As you can see, there are plenty of great things with this game. However, I did find a few weak points that kept this game from scoring a 10.
At several points in battle, enemies will launch projectiles into the sky. These objects will fly into the top screen, and then fall back to the bottom screen toward either Mario or Luigi. Your goal is to smash the object with your hammer before it reaches your head. This requires super precise timing. If you time wrong even a millisecond, the object will hit your head, causing major damage and eating a huge chunk of your HP. However, when the objects fall toward Mario, they are lost in the space between the two DS screens. When the object exits the top screen, it immediately teleports to Mario's head. For me, it was very difficult to hit an item I couldn't see.
Some of the enemies become very annoying. An enemy can spit a projectile at you, and when it touches you, you have to battle the enemy. However, at some points you will find yourself battling the same enemy over and over.
Some of the scenes take WAY too long. I found myself listening to Starlow jabber for 20 minutes at one point. And, if you get a Game Over, you have to watch the whole scene all over again.
However, forget that bad stuff. They are all very minor complaints. This is a great, fun game that pretty much anyone, ever RPG-haters, can enjoy. I highly recommend getting it. This is a game that is definitely worth playing, and that is why I have given it a 9.0 rating.