Heretic
GT3 was the last one I played.
Since I have a 360 instead of a PS3, I have to admit I know little about this one. I vaguely recall reading that the one main flaw people had with 5 was along the lines of it taking a longer-than-usual time to build up a good garage and get into the bulk of the cool racing. I don't know if that means license tests or that it takes longer to build up money or that you're less likely to win a car from a race/series that will CARRY you to a lot of wins.
Sometimes I think about picking 3 back up or maybe buying 4. But I just don't know that I have the patience to sit through all the S-level license tests (the ones where you have to run clean laps of most of the tracks) again. Which I'd have to do even with 3, as I deleted my save data from when I was running through it.