Horror movies tend to take sequels and remakes to unprecedented lengths. How many films in other genres can boast eleven sequels and a remake, for example? Though some are good and some are decidedly not, one thing is for sure; they just keep coming.
I've decided to count only series consisting of at least three films (as of the end of 2013). Also, I've excluded a lot of the old horror series, such as Dracula and The Mummy, since those characters have appeared in too many other films to really pinpoint an "official" franchise. As for the Night of the Living Dead series, I only included those which had George A. Romero's direct involvement. I have also omitted series such as Alien and the Hannibal Lecter series, which are not always considered to be straight horror films.