Why are some horror films so terrible and some so good?

For example, Killer Klowns from Outer Space, Trolls 2, and Fear of Clowns are just garbage but The Shining and The Exorcist are clics. What makes the bad ones bad and the good ones good? And why are most of the really terrible movies horror films? I don't mean bad like Gigli, I mean terrible acting, awful "special effects", etc.