I have had an insatiable appetite for Gran Turismo 4 for months. I've only got one of the two disks for that game and when I hooked up my old PS1 to my TV, I couldn't get the scree to work right . I loved that game. I loved the car customizations, the graphics, the racing - all of it. And I had only played it single player, offline. I haven't tried GT5 but I've heard it sucks in comparison.
Nonetheless, Gran Turismo is why, when I eventually do get a new console, it will most likely be a PS4. Online issues be damned.