You have to realize their history though. The "Nintendo seal of approval" exists because the game market was filled with horrible games when they first started, so trusting some other dev with their IP, which could potentially be ruined by a third party. They have been making strides with this (see Hyrule Warriors), but considering the piles of garbage games on the app store, their aversion is understandable. On top of that if you could get Nintendo games on other platforms, their console sales would suffer. Plus, a touch screen would just be frustrating for platformers like Mario, only turn based RPGs seem to port well.