I'd say it does. Nintendo have a limited number of first party games they can produce (2-3 per annum seems about their capacity recently) and when all of those games are competing with one another for a limited market it's a pretty risky business strategy. Having a broader range of genres would not only encourage users to purchase multiple titles (because they give vastly different experiences) but also encourage a wider range of users to purchase the console.

Maybe I'm misusing the word. I meant niche as in a unique type of game (co-op/competitive 2d platformer)

lol NSMB certainly isnt a niche the co-op 2d platformer is there with rayman and LBP and they are good sellers as well, i wouldnt call the genre a niche either