During the Wii era the 3D and 2D Mario games targeted very different markets and both Galaxy and NSMB had incredible legs. I certainly bought both and felt they offered completely unique experiences. However, now 3D Mario is moving away from the single player platform/adventure genre towards a 'party platformer' which has traditionally been the niche of NSMB.

From what we know so far, I personally can't see the need for both games. Anyone else feel this way?

(Lets not even get in to why Nintendo thinks that in 2013 2D platformers and mini-game collections are the only genres needed to sell consoles.)

I think that when we get more news on super mario bro 3d world , we will see that the game is closer to galaxy than we think , and if it is I wil want to buy it , I alway thought to myself it would of been good if galaxy was a two player game ,

NSMB2 didn't cannibalize the sales of Mario 3D Land, and both are single player games on 3DS, so no. Donkey Kong has a chance, but everybody will boycott it for not being Metroid, so it won't be a problem.

I suppose its how you look at the overall package, i mean NSMBU now has the Luigi DLC which increases the longevity of the game. At present we dont know too much on Mario world other than a few demos, perhaps it has tons of levels and unlockables.

Kinda, i think if 3D World didnt release then NSMBU would sell 15m+ but i think each will sell 8-12 million.

I think actions that in the long run may hurt NSMBU's sales are the least of Nintendo's worries right now.

If so, does it matter?

SM3D impacted NSMB 2 sales though. It's obvious by the decline although NSMB 2 is not the best 2D game and 2D mario is getting redundant unfortunately.

I think due to the multiplayer it will. Multiplayer is a big feature in Mario 2D and it being in 3D will have a major impact imo.

You really think people are gonna boycott DK or is that a joke?  

"which has traditionally been the niche of NSMB."

*looks at the millions upon millions that the games have sold*

you call that a niche?