Muckyai,
Indeed there are some crappy ones out there. I once read an article (cannot cite the source) but as I recall, it conveyed that horror movies were generally thought of as a "sure bet" by film companies to make money. Not hoards of money (unless it hit big) but generally they don't lose money. So, many "new" folks will create horror films to break into the business with lower budgets and lower risks.
The Shining was a great one I agree. Kubrick was a master at his art. Do a youtube search on The Shining and you will find scores of vids that try and pick apart hidden messages implanted by Kubrick, the same with his last film Eyes Wide Shut. Not to imply I believe it all, but does make for some interesting thought...
One of my favorites is Evil Dead II. Part horror, part comedy and had some groundbreaking cinematic techniques that were quickly copied by others. The premise has lasted for years and I saw something recently with the star (Bruce Campbell) playing his role in some new series.
John Carpenter has made a few great ones as well. I saw one years ago on television that particularly disturbed me called Cigarette Burns. Very warped.
There was a film maker in the 60's and 70's named Herschell Gordon Lewis who turned out some really weird ones. Graphic violence and tons of blood. He pioneered the use of "waivers" that had to be signed to get into the theater to see his films. Personally, I don't care for them, but in their day I can see why they made money. At least one film, 2000 Maniacs was (somewhat recently) remade by a Metal rocker named Rob Zombie.
I wanted to query the cops I work with to try and find out more about the new Halloween movie, but have heard that some non-disclosure agreements were in play, so I won't bother.
Just tonight, my girlfriend and I watched the new version of IT. Not bad. I will admit that there is something inherently creepy with clowns...