GT3 is a brilliant racing game. It's fast and furious, and has tons of extras which you can unlock and discover as you plough through the game.
The graphics are superb and the tracks meticulously detailed. The only grouse I have with the graphics is that the cars don't show damage (or at least do so very poorly). This tends to sap a little from the realism of the race but believe you me, you'll be so caught up in the blinding speeds that you won't bother about your car or those of your competitors.
You won't find a better racing game out there for the PS2... well, at least until GT4 is launched!