GT3 was my motivation in getting a PS2 in the first place, although some of the license exams made me want to gouge my own eyes out (I never got the S license due to laziness). Between GT4 and Forza there should be no shortage of wheels.
It took me 2 or 3 days or constant playing to finish that damn S License. Thankfully you get to carry over some of your licenses to GT4 if you have a GT3 save. That and 100k.