You’re tryingg to push water uphill. Vampires are immensely popular, and have been for over two hundred years (the legend is much older than that, but pop cuilture vampires with many of the features we recognize date from about 1800). They are convenient symbols and images for all sorts of things – represed sexuality, clas warfare, kids’ yearning after adult privileges, terrors of the night. If Vampires didn’t already exist, people would create sometyhing else to hang stories with these themes on.
Similarly, zombies as we now know them date back to circa 1960s films, crystallizing with George Romero’s Night of the Living Dead. There were zombies before that, but this gave us the flesh-eating predatory zombie. And, again, there are to many themes it introduces that resonate with people – alienation, persecution, etc. Plus they’re really useful all-purpose Bad Guys that are easy to realize on film with minimal efects. And kiling them is so cathartic.
Comic Book Heroes, as you rightly place them alongside this list, are also incredibly unreal. But they fill a niche. They’re mainly empowerment images for kids, who don’t have power in many forms. They’re wish-fulfillment images. The way they act and the things they do are dictated by their audience and medium – superheros fight supervillains but nobosy ever gets seriously hurt or bloodied – it’s approved, non-dangerous violence that they can recover from and go on another day – just like the coyote in Road Runner cartoons. Their gaudy colors and costumes are appealing to young readers and (just as impprtant) were brightly visiblre on newsstands. Things got grittier starting in the 1960s when they started trying to make superheroes more “real”, but that simply added to the [possibilities for more interesting stories. Marvel’s “heros with problems” in the 1960s lead to heros with serious problems and shortcomings in the 1970s and beyond, and eventually you get things like [ui]Watchmen*.
You might be grateful if all this was wiped from human memory, but lots of people wouldn’t. And it would simply be replaced with something else. In the 1950s you had crime comics and horror comics. In the fictional world of the Watchmen they had pirate comics. Would any of this be different, or preferable? I think we’d simply have different myths. In an alternate world, you might be railing against the prevalance of the damnned sexy Succibus and Incubus movies, or those Manticore comics.