http://iwataasks.nintendo.com/interviews/#/3ds/super-mario-3d-land/1/0
Koizumi: Early on [in the development of Super Mario 3D Land], we established the theme of making a 3D Super Mario game that would be close to 2D so that anyone could play. One big difference between 2D and 3D is the camera. We made adjustments as we went to the parallel-track camera we used in Super Mario Galaxy 2 so it would be easy to play.
Iwata: A parallel-track camera moves in parallel to Mario at a set distance
Tezuka-san, you were in charge of 2D Super Mario games. The 3D Super Mario games have always been Miyamoto-san's sphere, while you were in a position slightly removed from them. What made you become actively involved this time?
Tezuka: I never said much with regard to the 3D Super Mario games so far, but I sensed there were a lot of 2D Super Mario elements in this game, so I had things to say. I was like, "Let me chime in!" (laughs)
Koizumi: Well
I thought, "At last, we motivated him!" (laughs) This time,
we were putting aside the game element we carried on since Super Mario 64 of searching and were trying to reconstruct the game with the original Super Mario elements. I think perhaps that is why Tezuka-san couldn't help but feel as if it flowed like a 2D Super Mario game...
Miyamoto: ...In Super Mario 3D Land, Mario can change direction while he's in the air. That is an impossible action in the real world, but it was incredibly important
It was satisfying how, once we had corrected Mario's movement like that from the point of view of the players, it felt more like 2D Super Mario than 3D Super Mario. That's why Super Mario 3D Land is a 2D Super Mario-like 3D game. I think we can do a lot with that in the future
Super Mario 64 DS sold about four times as much in America as in Japan, so a lot of peple who play games in America are used to playing 3D Super Mario. Against that background, it isn't exactly wrong to say, "Super Mario in 3D is difficult, so we made an introduction that is like 2D Super Mario," but that isn't quite trueit's just that not everyone is used to it yet...