Scariest movie you know?

I'm looking too see the scariest movie you guys can think of. I just watched the original nightmare on elm street and while it was a good movie, I didn't find it scary. I've seen Texas Chainsaw Massacre and Poltergiest but neither of those were scary either... I can't really get myself to be scared because I always know it's a movie and that just takes away the fear so it's gotta be a movie you really get into. So what's the scariest movie out there? Also I'm just wondering, is the exorcism a good movie because I know that's supposed to be scary.