If you look at Buster Keaton or Douglas Fairbanks movies, what still amazes you today is their physical ability. The only special effects that never grow old are what you can do with the human body.
It is important to consider that the horror movies should - like modern art - not have a too obvious meaning. When you watch them, it is more important what you feel than what you understand.
Everything in horror film is about transgression, and the young audience wants to touch something that is forbidden and is, by function, anti-establishment. It is a way for young audiences to express rebellion and also to deal with very modern fear but in a very playful way, in a very symbolic way.
It is interesting: in France, the horror films are not so popular. People go to see them, but not for the same reason. It is more artistic and process.
