For someone that doesn't really play too many games I don't see this being an issue but for hardcore gamers I can see how they could be overwhelmed by the sheer volume of titles being released. They probably want to get hands on time with as many of the AAA titles as they can but probably struggle due to rate at which they're being released.
I get that, I'm not saying it would happen, this will NEVER happen. I'd just LIKE to see it happen, I'm simply pointing out which Nintendo franchises would work really well on iOS.