Apple should be offering gaming level hardware (i.e. you can build a very decent gaming system for as little as $1200 on a PC. $2000 would get you a system that a $3000+ Mac Pro couldn't touch with a 100 foot pole). OSX also needs support for things like SLI if it ever wants to even REMOTELY keep up with Windows.
While I agree with most of your points, I'm not sure that the very high-end should be Apple's first stop when it comes to gaming. These days, even average hardware can offer a very satisfying gaming experience, and while Apple is certainly more expensive than most for the same performance level, their current hardware is more than decent.
For instance, I've been playing on a quad-core 27" iMac, and all recent games I've played (Dragon Age : Origins, Mass Effect 2, Call of Juarez : Bound in Blood) ran very smoothly at max detail and max resolution (2560x1440).
It might be better for Apple to worry about actually getting some games on MacOS before trying to compete with the "ultimate" gaming rigs. I've got a feeling Windows-based PC will remain the undisputed masters for that segment anyway, considering the premium you have to pay for Apple hardware ...