You'd want to look at REZ and compare it to other titles of the time and before it, and then other titles that came after. You'll then have a basis of comparison for what the game did differently and how far it stretched the machine it comparison to later titles which show what the machine was fully capable of.
Also, it was a DC game as well, so cross-platform between two very different machines. Chances are it wasn't leveraging PS2's strengths in a big way, though I don't really know the game beyond its reputation as a trancey hip-fest shooter.