Great in nearly aspect except it can get frustrating very quickly when you have 3 or 4 people
The gameplay (important part) is where new super mario bros exceeds. Not only does it have many nostalgic features, but it also has new creative and innovative features. The most apparent is the obvious inclusion of multiplayer. Having fun with friends playing a mario game that is not a spin off is great. Though it can be very frustrating at times especially when you have people that are either new or poor at playing the game. And when they simply hold the entire team back or even worse just float in the bubble throughout the level using up powerups. Speaking of which the new powerups are a huge disappointment, the ice flower is just the penguin suit without the slide feature and the spin hat is a very cheap way to fly compared to the cape or raccoon suit. Though the new hat is necessary, you don't want to kill your friends, do you? Overall the gameplay gets a 10/10.
Now I was only able to get past the first 3 worlds and I played a few free for all levels, but the levels go quickly and I believe that game can be beat in roughly 15 hours. Replayability will simply be playing with different friends or collecting the star coins you missed.
I will simply not peak about the ver dumb story for Mario games are not known for their story.
Overall the game is great ir not perfect in nearly all ways except the frustration and tension that builds quickly when one person is doing poorly. The best thing is to just laugh it off and lastly is the lack of making your own levels and posting it online similar to Little Big Planet. Maybe with dowloadable levels from Nintendo it will be a game you can continually replay.