Agree Stephen King's earlier stuff was his best. His output is massive and the individual volumes very hit and miss: some brilliant and insightful narratives which tap into very American-specific anxieties, balanced off with some horrible, clunky writing and dubious social attitudes.
You've got to love The Simpsons and their total mockery of the 'Indian' (ugh!) burial ground as a tired old trope. They did a great number on Edgar Allan Poe - King's favourite source of inspiration - with Bart as the raven, too.
Talking of authors who should have their hard drives checked - step forward that other American horror writer, John Saul! He's like a King equivalent for a YA audience (the age at which I read him), with an unsophisticated writing style to match. But he's fixated on teenagers, and his plotlines are some of most twisted, disturbing shit I've ever read. That goes beyond the likes of Pet Sematary - which even King himself thought might have gone too far - into some really gratuitously dubious stuff. Some of his books made me want to scrub myself.
I haven't read much Dean Koonz. I quite enjoyed The Eyes of Darkness, but it was very obviously modelled on King's Firestarter.
Anyone read any Shirley Jackson? She's one US psychological/horror/Gothic writer whose work seems to be making a big comeback lately. We have always lived in the Castle is quite an entertaining read, but Merricat is a psychopathic protagonist to rival anyone in Saul. She's horrendous!