Also,
* DC had twice the video RAM as PS2 and this can clearly be seen in the quality of polygonal textures in certain games. DC, unlike PS2, also had anti-aliasing which showed in games such as Dead or Alive 2
* The DC version of Half Life, to my recollection, was a lazy and unfinished PC port, i.e. it wasn't created specifically for DC and therefore wasn't optimised for it. Look at PC/360 games ported to PS3 for a current-gen illustration of this
* Perhaps if DC game coders had enough years to fully exploit the system it would have seen even better games 4+ years into its lifecycle. Recall how piss poor PS2 launch titles were relative to games released years later