So 1978 is my answer every time someone asks what is the best single year in horror. I don't think it is even close really. Not only does it have 2 juggernauts one of which is my favorite horror film of all time it has several excellent to solid films as well.

Dawn of the Dead
Halloween
Grapes of Death
Martin
Long Weekend
Piranha
I Spit on Your Grave
Toolbox Murders
Alucarda
Magic
Invasion of the Body Snatchers
Blue Sunshine
Patrick
The Fury
Mountain of the Cannibal God
Redeemer
Jaws 2
Damien: Omen II
Jennifer
Killer's Moon
Someone's Watching Me! 
Eyes of Laura Mars

What is your favorite and if you could list the films from that year you like?