I don't know if Apple would try to target the strongest console maker as their competitor. If you take that route, you'll only be a second leg. The Xbox, although having a fairly unique library, was mostly bought by the same sort of people who bought PS2s (save for RPG fans), and now we're starting to see the same with the HD consoles. Similar userbases divided by fanboyism.
So while we would see two different potential userbases with an appreciation for innovation (and maybe a few casuals), it would mostly be Apple fans seeing Nintendo as their new enemy. Trust me, they're ready to make the transition from computers to consoles, even if they have no intention of playing them.