Since when has violence in video games been measurable? Pffft.
If I were to cold bloodedly shoot 100 people in a FPS with one shot but then hack up 10-20 goblins with a dirty great axe in a PnP RPG so that no limb remained in tact - which act would you say is more violent?
Whilst logically one might claim that due to the higher mechanical nature of the body count, the FPS deaths were more violent. Another might counter that because of the meticulous manner of psychotic dismemberment on the part of the goblins, the PnP act is the more violent. Both are conceivably true depending on your point of view.
I don't think these kinds of questions have an absolute answer which just gives me the desire to play Carmegeddon with the kind of mentality which thinks that there is.