I think the obsession with zombies is caused by the ease of creating an atmosphere when we play games or watch movies with them in it when were alone, as well as the room for inovation still present for the multiplayer co-op games with them as well. I also think its because of the variouse hallmarks in the genre, Romeros day of the dead did somthing new with the genre that had never bin done befor, the movie explored the nature of a zombie and made it all the more creepy when theive bin more humanized, and 28 days later made it evident that zombies dont exactly always fit the same mold even though the creatures in the movie werent technically zombies, and one final thing is that I think is the whole concept of it all, your in a world where millions of people want nothing more but to eat you whole and theill do anything to do that while your alone or with the last few hopefully sane people on earth is just somthing that never gets old.