There are only a few franchises in the gaming industry that you can name drop and everyone, instantly, knows exactly what you mean. It's like Tetris, or it's a Doom clone, or, in many cases for handheld games, it's a pale shadow of Super Mario Bros. These practically need no introduction, and New Super Mario Bros. continues that proud tradition.
Other than porting over some of the plumber's moves from Super Mario 64 (butt stomp, wall jump and triple jump), this plays just like the classics you remember. There are eight worlds, divided into separate stages that contain power-ups, hidden exits and a bevy of colorful enemies to stomp on. At the end of each level, there's even a flagpole to scale, just like the original NES game that inspired an entire generation of gamers and developers.
If it's relatively unchanged from something we all played 20 years ago, why bother? Well, if Nintendo can get one thing right, it's a side-scrolling Mario adventure. New SMB still has that magical sense of exploration and broad range of environments to keep the turtle-stomping and block-busting interesting. These games routinely challenge you to think outside the level, and consider multiple ways to reach the end - that means hours of fun.
Then again, it's mere hours that it'll take to put Bowser back in his place and rescue Peach once again. If you're good, you can completely wipe this out in one day, secret worlds and all. The fact that the game practically hands you extra lives on a silver platter only makes it easier - not a complaint, but tougher bosses would have been welcomed.
Length aside, there are still a few other weird issues that cling to the game. The three new power-ups don’t add much, and in the case of the blue turtle shell, are more likely to be avoided than sought after. The mega and mini mushrooms are fun to play around with (growing huge and shrinking, respectively), but aren't useful in a consistent way. Thus, you're left with just the fire flower - there isn't even a raccoon tail/magic cape to fly with, a series highlight that will be missed.
But what New SMB lacks in the single player, it covers up with a sweet two-player versus mode. You each control one of the Bros., and run through specifically designed levels in search of stars. Whoever gets them all first, wins. Grabbing them isn't the problem, though, it's keeping them. You can jump on the other guy to make him drop a star, or toss a fireball at him, or even nudge him into a bottomless pit. One notably cool moment was Luigi eating a mega mushroom and tearing through a pipe maze as tiny Mario hopelessly tries to stay ahead of the shredding plumbing, chasing his bouncing, escaped star.