How many horror movie series start with a good movie and then just get worse and worse? I'm talking mainly horror movies that move past the "trilogy" stage, like Halloween, The Exorcist, Hellraiser, The Texas Chainsaw Massacre, A Nightmare on Elm Street, etc.
What sets the Friday the 13th series apart is that it started in mediocrity and continues in mediocrity. No one has ever been disappointed by a Friday the 13th movie; each and every one delivers exactly the same thing. A friend of mine, a beer connoisseur, once explained to me that even though Budweiser beer is bland and horrible, it's apparently a difficult task to continually brew beer with the same taste. There's something admirable, even comforting about that. When one comes to a Budweiser or a Friday the 13th movie, one attains the illusion of stability in an unstable world.