It is hard to rank the best horror movie, there are many factors that go into deciding that.
Yes.  I agree that.  What is your favorite horror movie?
I do not have a favorite movie, but the movie Halloween is very popular.
Yeah.  My most favorite horror movie is conjuring.
The conjuring was apparently based on the Perron Family. 
Yeah.  Conjuring is based on a true story.
Other horror movies based on true stories include the Exorcism.
Yes.  Exorcism movie is very scary
Real exorcism can only be performed when the Vatican has given permission to do them.
Really?  That is interesting.