Okay here goes...
So, taking the usual suspects as a given - The Exorcist, The Shining, Alien, The Thing, Dawn of the Dead etc. etc.
Asia: J-horror is hugely over-rated IMHO. My take is that it was hyped up as the next big thing and then a bunch of critics leapt feverishly onto the bandwagon. However... The original Ringu is worth a look and is infinitely better than the US remake (ignore anyone who tries to tell you different
). also, check out I Saw the Devil, from Korea.
The Americas: del Toro's Cronos is possibly the best vampire movie ever made.
Europe: Let the Right One In is possibly the best vampire movie ever made.
Australia: The Loved Ones is good. The Babadook is creepy as hell.
Early German cinema: Both Nosferatu and The Cabinet of Doctor Caligari are pretty essential viewing for horror aficionados.
Overlooked gems: Philip Kaufman's 1978 remake of Invasion of The Body Snatchers is awesome. Polanski's The Tenant is one of the most disturbing films I have ever seen (I mean that in a good way).