And to be more specific:
Super Mario 3D Land is basically a dumbed-down version of Super Mario Galaxy, without the cool gravity effects and creative level design.
I don't think I agree. Of course handheld games are less expansive and maybe a little less complicated, but that's because they should be. What I want from a handheld game is something which is snappy, easy to pick up and play, and which keeps in mind the control limitations of the system and is, therefore, designed around them.
For me Super Mario 3D Land was an almost perfect handheld Mario game. Does it share some DNA with the Galaxy games? Well, yes, at least aesthetically; but I certainly don't think of it as being dumbed down. I think the people behind 3D Land showed a great amount of intelligence. They managed to take the essentials of a 3D Mario game, marry it to some of the mechanics normally only seen in a 2D Mario game, and in the process created something which can fit comfortably into neither category. More important than any of that though, the game is packed with delicious little levels which are just as smart and fun as anything we've seen on a home console.
For me Super Mario 3D Land is as successful at being a handheld game as the Galaxy games are at being console games.