You might have been using high-end hardware; you'll have little or no lag problems with that...
Lol, I wish.
AMD Athlon 64 Processor 3800+, MMX, 3D Now, 2.4GHz
512MB Ram
nVidia GeForce 6150 LE, 256MBs.
It's an alright computer but I usualy can't run any game higher than 800x600.
And that's with my graphics card on very low settings. (High Preformance, no AA, ect..)
Adding more RAM (i.e. 2GB) and a more expensive video card might be the reason why some people managed to play a GTA game (or any other game) in 1024x768 and higher...