If you cared. Lets take a look at these newer games. It would be difficult to make that more clear. You take the perspective of a well trained killer, and you kill. Usually, you kill other people.
Lets make it look worse.
In most of these, you kill for no real reason. Hell, in Kingpin, you kill to be a better criminal. Yeah, sure, each game has a plot, but most people playing don't even know the plot, they just play so they can go around killing. Ok, that's about as bad a picture as I can paint without getting silly. Heh heh, I like to kill people.