I’d largely make a list like Moth3r’s. There a lot of great scares in there.

I would probably drop The Orphanage and/or The Others as you get the same kind of gentle scare from The Devil’s Backbone.
I also don’t find The Conjuring that scary for something similar but more weird and unnerving I would watch either the under rated second Amityville movie or Burnt Offerings or Let’s Scare Jessica to Death
I would add more Asian Horror like A Tale of Two Sisters or Spider Forest.
I would probably add Old Dark House in because it’s Universal but strange.
I would also make room for REC (the first one) because it’s the only found footage film that really scared me, it’s a much more satisfying film than Blair Witch.
Plague of Zombies, Mask of Satan and Masque of the Red Death are visually astonishing too. I’m not sure what I would drop to make room for those though.
And any list that doesn’t have Nosferatu needs Nosferatu in it.
The Haunting (not the remake) and The Innocents are also great Halloween films full of atmosphere. The list needs more Val Lewton. Everyone goes for Cat People I prefer The Seventh Victim but Karloff is amazing in The Body Snatcher or Bedlam you can’t go wrong with anything associated with him.

Over this period the long lost cut of Exorcist III will be finally coming to home cinema so that will hopefully still be making me jump at the right moment.