First off Nintendo and Apple are my two favorite companies.
Economically I don't think it can happen. But lets entertain a partnership on games. After all, Apple competes against Sony and MS just as Nintendo does. Plus Apple needs serious help in the gaming department, relying on handme-downs. There is a lucrative gaming market that Sony and MS are feeding off of.
Now the most obvious benefit to both companies is all games that run on Macs also run on the wii and all wii games run on Macs. Technically speaking they are two different beasts.
Running wii games on Macs: Games that take full advantage of the wii are too graphically intense to play on even a powermac let alone a mac mini. The wii was made for gaming and the Mac was made for photoshop. Even if wii games could run on a powermac, they still could not run on a mac mini with shared ram. Powermacs are sold to profesionals, not gamers.
Running Mac games on wii: Resolutions are different between the systems. The wii is made for sd tvs which are 480p only. Vary few games that come to the Mac run below 1024x768 so the Mac games that you play will be downsampled, you won't get the full game. The succesor to the wii will probably be 1080p, but that won't happen till at least 5 years from now. By then computer resolutions will be higher than today.
So as much as I would like to see Apple/Nintendo beat MS, drastic changes would have to be made to make it work. The most I could see benefiting from a partnership is a portable ipod/ds combo where they set the standards. The standards have already been set on tvs and computer monitors.
(sorry about reposting bits from other posts, I just wanted to see it all come together)
n8mac