It is definitely not the Worst, but is just mediocre in my opinion. Having tried my PS2, X-box, and stand alone Pioneer DV-C302 I can say there is little comparison between a game system that plays DVD's and DVD player.
I am also sure that the connection type you use will enter into the amount of difference.
RF-SUCKS any way you dice it
Composite-Better, little if any differences in DVD and PS2.
S-video-Good, will see large differences in DVD and PS2
Component-Awesome color, night and day between DVD and PS2.
You need the updated drivers. If you haven't bought a system yet, get one with the "R" designation after the model number. If you already have one, purchase the Sony remote control with updated Driver in it. You'll need 2MB of empty space on your memory card. This will lessen the amount of problems with compatibility as well as adding more functionality.