The subject matter has had a pretty skewed representation in movies. Thomas Harris is mostly the one to blame, he set a standard with his work that everyone else more or less followed, a standard of writing that produces fascinatingly disturbing characters like a well-oiled machine, that unfortunately have very little to do with actual serial killers. His characters might as well have demon wings and fangs for how realistic they are, but somehow these overblown caricatures prevailed in fiction, perhaps because it is easier for normal people to come to grips with characters that are so incomprehensibly evil that they might as well be from another planet. I have nothing against "monster movies", they are a fine distraction while you stuff yourself with popcorn, they are just a bit too easy to forget once you close the book/leave the theater and your spine stops tickling.
Is it just me or does one of the guys from Funny Games look like Trey Parker of South Park?