What do you think makes the scariest movie?

In my opinion, the whole blood and guts and serial killer thing isn't scary at all. Maybe if it shows up randomly at your window and stuff, then it's a little scary, but after that, it gets boring. I think that the scariest movie would be about the supernatural accompanied by disturbing creatures hiding in the shadows. I think the scariest setting ever is in a hospital. If a person were in a hospital for a few months and started seeing disturbing and twisted things then is followed by them when they are better and go home,that would be an awesome movie. Something like a mix of demons and The Hills Have Eyes deformed people. The grotesque demons could keep scaring the person until they reach the brink of insanity. The person gets some idea that if they kill, they can satisfy the demons and they will leave them alone. The person goes around stalking people and killing them quietly. Despite the wild idea, the demon activity increases. The person loses all grip of reality and commits suicide, only to find themselves waking up at home with a spouse and family they don't remember. They find out that they've been in a coma for 2 years and had been paralyzed from a car wreck. The person is cared for by their "family" only to find out that they are demons. The person keeps switching between twisted realities with disturbing images and events with the demons. I'm not sure how it would end, but I think that'd be pretty creepy. Like a giant fever induced nightmare with disturbing hallucinations that you could never escape. What's everyone else view on "scary"?