That would be from Iron Maiden's instrumental, _Genghis Khan_, on the _Killers_ album. One of the greatest metal albums of all time.
The riff is almost identical, apart from a slight tempo change. The other thing is that while it's the best thing in that awful Papa Roach song, it was only one minor part of a fantastic Iron Maiden song, that is itself merely a lesser track on an incredible album. Kinda funny.
I've been loving the depth of fun this game has. What I haven;t (yet_ enjoyed is the feeling that it requires repeated beatings to max out weapon and health levels. Though in small chunks I could see myself tearing this game apart.
I had a lot of fun with the demo, but after fifteen minutes or so of button-pounding action my right thumb couldn't take any more. There was a list of combos tucked away in the help menus somewhere, by the way.