Worth a look but don't get your hopes up too high.
The story stay mainly the same, Bowser has kidnapped the Princess and it's up to you to get her back again. The levels in New Super Mario Brothers have many references to the previous game. There are 8 worlds with different geographical settings - e.g. Snow land, Cloud land - each with around 10 levels and 2 bosses. You could finish this game in under 5 hours. Nintendo have failed to put any good reply value in this game as you can play the game hundreds of times and you will still play it the very same each time. The closest thing they did was to collect 3 coins from each level, these coins can be spent on new path ways and background images. There are no unlockable mini-games or characters leaving the player very unrewarded. Don't get me wrong however I thoroughly enjoyed my experience with New Super Mario Brothers.
The colourful detailed graphics brought Super Mario Brothers to modern day gaming beautifully and could easily be on of the best looking DS game around at the moment. Though close up you can see that Mario uses only a few pixels and leave it very weird squarey look too it. It has very Mario styled music and sound effects and has the original 'end of level' sound effect if you complete a level with a certain amount of time left. The sound effects do not get too repetitive and i ended up not noticing them.
Once you have completed this game you will expect there to be more mini-games to be played etc. but almost all of the mini-games came straight from Super Mario 64 DS and was kinda lame when i found i'd played these already and my high scores were on the other game. You will most likely decide to trade in or sell this game once your finished with it because of the lack of end of game features. There is a very fun fast paced multi player, this is off line and for 2 players only. One of the mini-game features there are is that they can be played up to 4 player.
New Super Mario Brother has it's problems but when you get down to it, it's a fun adaptation of the original Super Mario Brothers and well worth a look but don't get your expectations up too high.