Okay, what's the game that has the more gore? That is Soldier of Fortune II: Double Helix. You can shoot off parts of someones face, their body, their arms, feet, hands. It is the only game that has such a highly detailed level of gore.
Manhunt doesn't. Manhunt is disturbing but beyond that, most of the violence is implied. Really, the worst thing you can do in Manhunt is decapitate someone. Everything else is implied. Okay you stab someone in the eye, right but you don't see the gaping wound, you don't pull his eye out ect.. Really, I'd say Manhunt is the most disturbing game rather then sheer gore.
As for Postal, sorry but the graphics in postal are too terrible to even be considered. It's cartoony and awkward and by no means highly gory.
SOFII is in reality the game that contains the most gore.