I hate to be another "this game is perfect" person, but well... I love it. The best platformer game. This is my youth.
The graphics are not necessarily the greatest now, but in its heyday this game was quite well done. Better than games that came after it on the N64. The graphics are well done enough that you don't cringe in pain. They almost seem as timeless as 2D games. Also, the sound in this game is pretty impressive. From Mario's "Wahaaaa" to Bowser's roar I always found that this game didn't make me want to race to my CD collection.
The controls, which were admittedly a tad bit frustrating with the camera, but in comparison to other platformers this game managed to make it pretty easy to pull off 3D jumps, walk across thin beams, and performing wall jumps.
The story is deep as every Mario game. Save the only girl in town, besides Daisy, of course. Do this successfully and be prepared to feel the wrath of Bowser. The Bowser battles are fun and interesting. I liked every battle from end to finish.
I of course saved the best for last and that is the level design, which in my mind is amazing. I believe I read this in a EGM. They said that every level is different and memorable. When i looked back at the game, I completely agree. I don't even have to play the game and I can go through the general order of the levels. I have a terrible memory, by the way.
You don't have to buy this game, but if you want to be respected by any fellow gamer, then you'd better consider buying it.