Lets take this absurd topic to its logical conclusion: why would I, a PC gamer, ever bother with the PS4 and '720' when 95%+ of their games will show up on it, almost certainly with better controls and better visuals, no fees for online play--and on dedicated servers, at that--none of the issues with backwards compatibility or having my games locked out because SONY, for example, decided that I'll have to keep a working PS3 for *eternity* to keep playing all my DL content, and game prices that are, in general, substantially less, particularly over time, than on those machines? Seriously? Why bother with those machines unless you must play Uncharted XIII or Halo IX? And the answer? The same one you'd get from your hypothetical about which games you'd have to buy a U to play.
The point is, duh, it's about exclusive content, and until Nintendo games show up on some other platform, I'll be buying every NIntendo platform from here until the day I die, which is not the same for Sony and MS' next consoles which feature *exclusives* I just dont' care about.