The problem I see is that the game market is over saturated as is. Especailly with Nintendo seemingly revitalized in popularity with the Wii really starting to take off. Then you have the XBox 360, which Microsoft will fund forever.
The PS3 is off to a slow start, but by the time Apple could really mobilize into the game industry, the PS3 will be cheaper, have its userbase going, and have a wider variety of software as well.
A Nintendo-Apple alliance would be nice ... but honestly I think the question is, how does that really benefit Nintendo? Especailly since they're a notoriously controlling company (as is Apple). I don't think it would work. If Nintendo wanted to do things like a set-top box version of the Wii or a Wii 2 in the future with say TV recording functions and music playback, they could do that themselves. The Wii already can (or will) do things like have a weather channel, news channel, display digital camera photos, surf the internet, send/recieve e-mail, etc. So even Nintendo has eased off their "game-only" approach of the past.
If Apple wants to focus on something, IMO, it should be towards making the Mac Mini that really interfaces with your television and can do things like record TV right out of the box, with a stylish design and an affordable price.