Up to a point for pete's sake! After a while you want to return the favor. Nuke some evil martian zombie ass and move on w/the narrative!
Have you done all the levels? Recruit, marine and what not? I hope your link helps. I tried some other info I got on the web and no luck.
I have really been wanting to try the JAWS one. The beta was supposed to be great but the actual one had really bad reviews.
I also tried George Romero "land of the dead / fiddler's green" but even when you shot the zombies in the head they didn't fall over. So of course you can guess what my eventual digital fate was.
A snack for the undead.