I'm glad this thread has been brought up. I've been aching to explain this to people for some time.
Yes, vampires and zombies are losing their 'scare factor'. However, i might argue that it's not just pop culture that's killing them off, but the fact we live in a desensitised and globalised society in which we are being exposed to more and more avant garde things, that monsters such as bloodsuckers and walking dead no longer hold such a significant threat to us. We're more concerned about muslim extremists and young people stealing or stabbing you in the street.
Back on topic, i would argue, in the case of zombies, that it is because they have lost so much of their mystique. Gone are the days of "zombies rising out of the ground for absolutely no reason and consuming the brains of the living, for them to join the ranks of the dead truly brainless", as the irony may be. No. Now it is all about "viruses" and other "logical explanations" - take Resident Evil (film and game) and even Left 4 Dead, which is about a rabies virus. And 28 days later. They're not zombies, they're just mentally damaged folk who have gone feral. That's how i see them. Not as the reanimated dead. I think the movie and game industry needs to find a way to stop explaining the appearance of zombies in rational terms because it humanises them to the point of us no longer associating them with the living dead full stop. The fact most "modern" zombies now run and can almost think also contributes to this humanisation. It's atrocious. Look at "night of the dead" - slow, unthinking, mindless zombies that came out of nowhere and had no thought. Nothing. That is what they should have remained.
On to vampires. Now, i'm not big on vampires in general, i won't admit to having sat through Dracula all the way through, nor do i find them particularly scary or interesting as a concept. But there comes a time where i have to agree and say that pop culture has killed off the 'vampire'. In the words of moviebob, "vampires needed a new home now that they had become a fetish for sexually frustrated female novelists - thank you soooo much ladies". Not that myself or moviebob is making a sexist comment, but frankly, he's right. It's always some pathetic sappy love story woven into a vampire film and it's nearly always usually men. Why? Why does it have to be vampire men? This frustrates me to no end. If anything, it should be vampire women. Vampires typically were LUSTFUL creatures. None of this lovey-dovey bullsh*t. They hunger for blood and sex. Have you ever seen pictures of classic vampires? It's like an orgy of blood and bare bodies. They have no compassion. This is how a contemporary vampire SHOULD be. One may even argue that lust shouldn't even enter the equation at all. Seduction and trickery is what a vampire uses to get their meal, if they cannot overpower their prey. STOP TURNING THEM INTO PUSSYCATS AND MAKE THEM INTO LIONS.
Frankly, if you ever read a horror novel with vampires in, and then watch a movie with them in like Twilight, you'd think they were two entirely different beings.
I think Werewolves are probably the only unmolested creatures left, and i'm sure Hollywood will find a way to jack that up too.