Ok, so Mario manages to get his girlfriend kidnapped by Bowser and family for the 100th time. Mario goes to a grass world, and then to desert world and beach, ice, and jungle, or mountain in any order and then there is the sky and lava where Mario fights Bowser....along the why he fights the koopalings who are easy and take only 3 hits oh and mario might run into a boo hous..and zzzzzzzzzzzzzzzzzzzz
Yeah, this is my problem with the series. The only one that tries to be "new" is the Wii one with it's multiplayer. Other than that, it just a rehash of basic world themes with forgettable levels. It feels the same. This is a problem since the older Mario games played and looked different from each other and they tried new stuff. The New Super Mario Bros games, however seem content with playing the Nostalgia Card and assuming that gamers would be too entranced by nostalgia to overlook the fact the games are mediocre at best games that can't hold a candle to say Mario World or Mario Bros 3.
If you want a platformer in the modern ages, go get Little Big Planet 2 Donkey Kong Country Returns and Tropical Freeze, or the two Rayman games. If not, then there is a whole library of platformers in the past that could provide a much better and satsfying experience that New Super Mario Bros can't provide.
These games are just mediocre forgettable games designed to appeal to nostalgia and nothing more.