Just boot into your BootCamp partition instead and give windows the whole of the Mac's brain. Morrowind works while in a virtual machine, but Oblivion and the Fallouts won't despite the gaming score showing as higher when Windows is run through VMWare than on its own. By the same token, the three above mentioned Gamebryo games will set their settings higher when auto-detecting from within a virtual machine (SLI) than a stand-alone, however they'll actually run (and run well) using solely the more powerful of the two cards as Windows will have it when it's got the whole rig to itself.
Something I notices with my MBP: Left/Right taps on the trackpad don't reliably register in gamebryo games while they do with, say, Dragon Age. I've found I need to use a mouse for 'em... If ever you figure out how to get the trackpad taps working in game, lemme know?