Umm are you guys serious.. I play GTA IV on my macbook pro using bootcamp all the damn time!! So does my friend with his $1500 macbook "pro". I mean the settings aren't on max, but they're for sure over medium.
As for San Andreas, I downloaded a torrent of the mac version (JUST TO TEST) and it didn't work. I believe it was a problem with the video card support or something. I had to manually turn off the power of my mac by holding the power button :[ So I'm guessing it doesn't work with the newer macs.. San Andreas works great over on the bootcamp (XP) side though, even with my PS3 controller! You should seriously look into bootcamp gaming, its awesome + loads of hacks and mods of your favorite games and on your favorite computer!!!!!!
Or... just get a PS2, they're pretty cheap these days.