I don't know, I bought my PS2 for one game, and that was FFX.
That's really the only PS2 exclusive game that I think stands out.
I guess the Silent Hill series and Devil May Cry was pretty good as well.
GTA San Andreas was really good until you get to that certain point where you just... don't want to hear about it anymore.
*shudder*
But yeah. Final Fantasy all the way. \m/