Ah yes, Jak and Daxter... I never played one since I heard it being rather lackluster (or atleast, too much of a platformer), but I've rented two time and again, and own three. I play it from time to time; my best (and only good) file was deleted by my idiot friend, though. -.-; That jackass... Had every damn thing unlocked.
Call me bland, but the games I play most on my PS2 are Kingdom Hearts 1 and 2. They're just brilliant games, the perfect beat 'em up for me, really. Even if the game's storyline seems built for a child, you can't deny the wonderful gameplay.
... I still dream of Kingdom Hearts 2: Final Mix + making the transition to english and being sold in the US... Anything that makes the game harder (considering how easy it is) creates an entire new game for me, and there is ofcourse, plenty of new features. Think of it how Platinum is to DP; but better.