I think the best story/concept go to A Nightmare On Elm Street. It was pretty much 100% original. A killer who attacks you in your sleep! The spirit of a psychopathic child murderer/molester come back to torment and kill the children his own killers. Very cool.
Before Fred Kruger you had real world killers like Norman Bates, Leatherface, Micheal Myers, Pam Voorhees/Jason Voorhees. Before the masked killer craze you had space aliens and invaders from 50's and 60's Sci-fi. And before that you had your classic movie monsters: Frankenstein, the Wolfman, Dracula, Creature.
I think Wes Craven really brought something truly original to the table with NOES. I dont think the film really gets the credit it deserves mainly do to the trash sequels that followed which took a great story and frightening villain and turned them both into pure crap.
Having said that, I dont think NOES is the best horror movie ever made, nor is it my favorite but I think it should be held amongst the best plot/stories/concepts to come out of the horror genre.