Under rated! the second Mario Bros. game was largely different from Mario's other games. Different dosn't mean bad.
Lets talk about the worlds. It's been a while but I believe the game had eight or nine worlds in it. All of which were usually a bit different then the last. There were two desert worlds, a ice one, sky world, then just alot of standard orignal worlds like the first if recalled correctly. Either way the worlds and levels were all fairly fun. From falling down thousands of feet in the sky from the get go of the game, to riding magic carpets, tunneling through giant sand dunes, crossing a giant vast bottomless sky by jumping from one bird to another, riding logs up and down riverfalls, to climbing giant bean stalks, this game had some truely different and awesome gameplay packed inside it's worlds.
Each world concluded with a boss battle. These fights were always fun and the hardest out of any mario game I can ever remember playing. The game has like four different bosses at the end of each world which you do fight some of them at the end of more then one world. The crazy gangsta mouse with the shades and bomb chucking frenzy problem was at the end of the first world and a two or three others. Though guys like the giant fireball guy at the end of the ice world(Ya a fire boss in the ice world go figure) and the giant crab in the water world were only fought once.
Jumping from one world to another was also in this game where you could get to the second from the last world in the second stage of that world in about five minutes if you knew what you were doing. Well at least that's what I was capable of. Maybe you could of skipped to the last level of the game I don't know.
The enemys in this game were all really fun and interseting too. There was a very large and diverse populatuion of enemys for a game back in it's day. Everything from little star dudes, seed spitting block dude things, whales, flying masks, do-do birds, nuke dropping birds, giant bombs(birds dropped these guys sometimes), electric orbs, flying faries!!!, and I'm sure there are more that I'm missing. Seriously though compare the enemy count in this game to something like Altered Beast, or any other game back in this time frame and you will find Super Mario Bros 2. has a very large amount.
Bottom line this game was a blast. Like I said I didn't get into it at first when I was a kid. It was too different from the other Mario games. It wasn't till a couple of years ago when I replayed it at a motel in middle of no where(Ya the owner had a pimped out NES) I reliazed how awesome this game was. Considering the fact the game put up a bit of a changgle unlike most other Mario games when played these days(they are still fun). As a kid only took me at least several dozen hours to beat it for the first time, which spanned over like three to five years.
Just because a game is different dosn't mean it's in a bad way. In this case it was a very great thing that saddly too many people seem to not reliaze.