That comparison doesn't work because Apple doesn't make any money off OSX. Nintendo on the other hand makes money off both hardware and software but their hardware margin is getting squeezed so they may consider selling software on other platforms.
The more apt comparison would be Apple not releasing iTunes for Windows and missing out on the iPods and later iPhones sales to Windows users. That's exactly what Apple has done despite Jobs' initial protest.
http://www.linkedin.com/today/post/...-the-butterfly-that-started-the-apple-tsunami
So a kind of a gateway drug to drive people into getting Nintendo hardware with proper games? It could work.
Just offloading all the game collection to iOS emulators and selling that on the app store seems a bit silly to me, though.