Shocking rather than frightening.
Friedkin's The Exorcist is a film that shocks rather than scares. A well made film that achieved notoriety via pea soup. A slow and intelligent film with strong performances - yet also a mostly disappointing one for those who dare to go beyond the hype and actually experience it for the first time.
For a film that does succeed in frightening the audience and with none of the hype - I recommend The Changeling starring George C Scott. Now THAT is a scary movie.