Whoa. A million replies. Looks like I've got some reading to do...
EDIT: Oh... it seems most people that were quoting me weren't actually addressing me... seems we're all in agreement that the "crouch behind something to heal" is the dumbest way to heal in any game. Except for the guy who sicked Wolverine on me.
The hookers from GTA are ridiculous and intentionally lulzy, but still an active healing method. You have to find a hooker and pay them. In God of War you have to find the babes and do your little button-tapping dance to gain health from them.
And yeah, Onyxmeth is right. None of these are about realism at all. The only realistic way to take a bullet to the face is to immediately die and never come back. So with realism out the window, I go for the healing methods that reward me for either beating up baddies and stealing their health, or finding health somewhere (usually in the back of a room full of baddies).
I just can't stand games where players are rewarded for hiding (aside from stealth games of course). You are being rewarded with bonus health for being a coward. It hurts multiplayer. People who hide to recharge should at least have their usernames as yellow as their bellies.
