These are some good flicks. I, too am a huge fan of horror flicks. However, for sheer disturbing cinema, I'd have to pick:
Silence of the Lambs
Cube
Blue Velvet
28 Days Later
Children Shouldn't Play with Dead Things
Don't Look in the Basement
The Collector
Henry, Portrait of a Serial Killer
American Psycho
House on Haunted Hill (50's)
Village of the Damned/Midwitch Cuckoos (60's)
Brotherhood of Satan
The Mephisto Waltz
Psychomania
Don't Look Now
The Dunwich Horror
Salem's Lot (The 70's TV Version)
There's a lot more, but I'll just keep it short.