I just installed GTA3 (i had it on an installation back like 3 years ago on my old Radeon 9550 and i loved it, but it was slow), and now i have it on my 7800 and its beautifully smooth.
and i realize
GTA SA was never this smooth. Even on my brother's machine with an E6550 and an 8800GT, its not very smooth at all. it runs fine, its just seems sorta like a step back in animation and 3d. Also i noticed, GTA3 was much more fun because of the detachable limbs.
i dont think SA was optimized very well, at all. its not nearly as bad as BF2 or anything but its pretty bad. hopefully GTAIV (in october) will be optimized well (like Crysis or COD4)