I never get bothered by gore in games because its only disturbing if you sit and stare at it, even in L4D2 even though their are quoted by valve 47 different places to shoot a zombie to cause a suprisingly violent fleshwound it doesn't really affect you within 3 frames of your kill you have 12 more zombies walking through the dieing zombie. Now, games like Manhunt can be seen as exaggerated but then again if you can't stand violence you shouldn't play a game that is called Manhunt and has a picture of some insane killer with a hockey mask on the cover. I do notice and am annoyed by games that are dark enough to require blood, games like Medal of Honor don't need blood since they are less dark and more cinematic, but try playing Unreal Tournament with gore disabled and see how quickly you give up.
As for realism, realistic gore doesn't really exist, if it did it would be lame, getting shot doesn't make blood spray out like it does, it can but normally they just bleed out. If you want realism watch a documentary, video games are fantasy, not simulators. There is no WWII nazi killing simulator, any gore is probably exaggerated. Saying that its a good idea to have every game load the "Bloody Mess" perk physics or the TF2 gibs isn't smart, but if you want gore in a game it wont be realistic.
Basically, if you want a shooting game and you are worried about the gore, instead of doing what the ESRB does to rate games by closely examining the amount of detail in each kill, just shoot and move, seeing some red pixels on a wall never corrupted children or destroyed the world.