Even seeing real life violence on TV isn't comparable to seeing real life violence. So basically...what jerico said but a bit different
Go watch some real life violence, in person, especially if people you know are involved, and see how you do.
I'll tell you, I have yet to be phased by seeing violence on TV, real or not, but seeing stuff go down in person, tends to bother me, or wreck me if someone I care about is involved. To me, sensitivity to violence is heavily reliant to how 'connected' to it you are, so your reaction to TV/Video Games/Movies isn't a gauge at all.
Getting between me and my morning coffee is suicide...