The Exorcist in my opinion is Horror Masterpiece i mean it's really hard to find another horror movie that has had a bigger effect on society then the Exorcist the movie is like 30 years old and it still holds up very well today just because the movie isn't all gore and fake blood doesn't mean it's not disturbing. When the exorcist was released everybody was going to church. This movie also has some of the most famous scenes in a horror movie like the girl's head spinning or coming down those stairs like a spider so in my opinion their is no doubt that The Exorcist is a Horror Masterpiece.
As for most of the others on the list I will agree with you on the fact that many of them are overrated but I can't get passed The Exorcist and some people not liking it. To me it's brilliant!