I first saw The Exorcist when it was released. The spinning head was one of the shockers at the time. I have seen it many times since, including a few months ago when they re-released it in the theater. Of course, it didn't have the same impact as the first time I saw it. BUT, as the years go on I still find it scary and here's why:

Firstly, the theme itself (demonic/devil possession) is a pretty scary topic to begin with. Add good acting (well, with the exception of Linda Blair....until the demon took over)Father Karras and Regan interactions were particularly good I think. Add to it the atmosphere of the film LIKE a room so cold you could see the actors breath as they spoke..totally creepy.. and to top it all off that horrible demon voice (Mercedes McCambridge). I likely won't see it again for a while. Let's face it you really need to be in the mood to see it right? Then again, what mood would that be?

TIS