Consistent updates with openGL. Support for more graphics cards ( GTX280, 4870x2) and multiple graphics card solutions, the implementation of SLI and CrossfireX. A Mac Gaming line (imagine Mac ProX or Macbook X, or some other lame name solutions to sell it to the masses, a black Mac pro with purple case lighting screams evil, though) and more opened drivers for both graphics companies. Less costly/exclusive/"uber-highend" parts, keep the Mac Pro case though
. A smartly designed Mac Gaming mouse and keyboard. More "gamercentric" options (user hardware upgradeability (who likes buying a new system just for a better graphics card), tweakable openfirmware (overclocking, etc). Apple or Mac Games library. Release a Mac home console comparable/better than the 360, integrate some of those great OSX features from the start (a dock, downloadable games launchable from the dock, safari browser, "low power" mode for non gaming functions, get creative with it). iGames (to contend with Xbox Live) anyone?
NATIVE GAMING, no bootcamp, no parallels, no Wine/Crossover, just convince devs that your products are superior.
Maybe I'm just dreaming too damn big... It could work though...
Also, quit trying to target college girls and business professionals. Target everyone.