Other then Carpenter's The Thing, this has to be my favorite classic horror of all time.
I consider Hitchcock's Psycho more a thriller then a horror though at the time of release of Psycho, I can understand why it would be called a horror movie(one of the most controversial of its age).
Halloween(Michael Myers) embodies humanity's dark side as well as evil so he's always been the better of the killers created by our horror directors of that era.