John Carpenter number one for me. I had the pleasure to see the guy last year. I have collected all of his movies and not a long ago I finally saw the Elvis movie which was the only one I was missing. The Thing is easily my favorite Carpenter film.
Other great has to be Wes Craven. I love what he did from late 80's to early 90's, Serpent and the Rainbow, Shocker and People Under the Stairs. And ofcourse A Nightmare on Elm Street is classic. There are couple of Wes Craven films I haven't yet seen.
And ofcourse David Cronenberg. The Fly was first Cronenberg movie I saw and I was probably around 6-7 years old back then. I think my favorites are all the films he did between 1981 and 1986, Scanners, Videodrome, The Dead Zone and The Fly. Few fantastic movies much later on, A History Of Violence and Eastern Promises. There's been a lot truly great films by Cronenberg. I have seen all but the few latest ones. I really hope to see Crash (1996) on blu-ray one of the these days.