The Shining wins for me. Oddly enough, it’s one of the few old school King novels I haven’t read - I went through a bit of an SK craze when I was 15/16.
My second choice was Misery, with Carrie as a runner-up, but mostly because I really liked the book as a teen. Cujo and Christine terrified me when I saw them as a kid (Christine especially), but I haven’t watched them since so I can’t judge.
I agree though that The body/Stand by me is probably King’s best non-horror accomplishment (IMO at least), both in terms of writing and film adaptation.