OK, if you want the best graphics, go buy Gan Turismo prologue. Almost Photorealistic. However, you race round and round and round a track. Pretty crappy if you ask me. Graphics - great... Gameplay - not so.
GTA is on the other end of the spetcrum. It doesn't rely on Graphics like Gran Turismo has to, because it's gameplay is surpassed by nothing. You cannot base your opinion of A game on simply screenshots, you can say it looks nice / crap, but that's about it. These screenshots are development screens. They have also had to have been captured from a console and ported to PC, which may not be the most detailed / accurate / efficient way to get good looking screenshots. In almost any gaming magazine, you get pixeltated screeenshots, but the final game, completed and optimised for your TV / monitor looks so so much better. You have to take more into account than: 'Screenz r shit so gaym iz 2'
On top of which, the graphics may have to be lowered for online play, as more processing power is needed to gain info from the game server, and transform it into things on your screen, and then having you be able to interact with them.
You were all blown away by San Andreas, Right? This is a next gen game, next gen console, next gen engine, next gen graphics.It' going to b awesome, no doubt.