Really fun, but way too short.
but the problem is that its too short and too easy (except for maybe the last level). I personally completed it in around one and a half hours. The game would be perfect if it wasn't for that.
The graphics are really good compared to the first, with larger and more detailed sprites, and the sound is really cool, especially the background music. The level selection works a lot like Super Mario World for the SNES, with an overhead map and secret levels for finding a different exit in certain levels.
There are 6 worlds overall, with each world consisting of three or four levels and one boss. Unfortunately they are (mostly) incredibly easy. Once you have beaten all the bosses there is one more level, Marios Castle, which Wario, Marios evil brother, has stolen. This is the hardest level in the game, but it still only took me 20 minutes to beat it.
If you lose all your lives you do not have to start the game over completely, but you do have to do all the boss levels again, which is extremally annoying, but you can get more lives or power ups with three bonus games. One is a slot machine, another is a crane game, and the last one is a weird line following one.
This game is worth getting if you like the Mario series, but once again, too short.