As long as the movie is fake enough with well known actors and CGI effects, I can't really take it serious or get creeped out by them. For me, most disturbing horror films cross a line or build so much suspense by what you don't see your imagination makes it worse (or better ;-) than u thought:
Disturbing:
1) A Serbian Film
2) Human Centipede (1, 2 & soon 3 :-/
3) Last House on Dead End St.
4) Cannibal Holocaust
5) Cannibal Ferox
6) Irreversible
7) Dawn of the Dead

Necromantik (1 & 2)
9) Aftermath
10) Salo: 120 of Sodom
Fear of the unknown:
1) The Blair Witch Project (saw advanced screening b4 it was trendy)
2) Paranormal Activity
3) Last Broadcast (Jersey Devil)
4) Rosemary's Baby
5) Snuff