The problem with the Saw movies is pretty much symptomatic of all of the issues in Hollywood right now with the horror genre. Movie Studios are incredibly afraid of taking any financial risks so they're only greenlighting sequels and remakes..
In Saw's case we have a movie that has played itself out and has nothing interesting left to offer. It's torture horror with some twists and by the time Saw III came out there wasn't anything really exciting about the series. In a way it's similar to how Freddy and Jason movies played out in the 1980s where the sequels were mostly about setting up new and creative death scenes and the plot as a whole was pretty much a carbon copy of the previous film.
The remake issue is even worse because they're remaking everything. They remade Japanese horror movies (The Ring, The Grudge, Pulse, etc) because they couldn't come up with anything new. They remade Texas Chainsaw Massacre, The Amityville Horror, Halloween and regrettably The Omen because those franchises made money for them before. There is even a Friday the 13th remake coming out in February that looks like pretty much any other Jason movie.
The studios' seem to have no qualms with dissing the fans of a particular series either. There's a new Nightmare on Elm Street on the way where there will be a different Freddy Krueger than Robert Englund. A new Hellraiser on the way with someone other than Doug Bradley playing Pinhead and even a new Candyman movie where not only is Candyman not Tony Todd, but the character will be a white guy, thus killing the entire premise of the story.
Hollywood has gotten so un-creative with horror they've talked to Wes Craven about remaking some of his lesser known horror films like Shocker and People Under the Stairs.
If it seems like they're getting desparate, it's because they are. Their unwillingness to take a chance on new horror stories, new horror directors and new horror writers has played itself out this way unfortunately.
This summer Clive Barker's short story, The Midnight Meat Train was supposed to be released with a wide screen release. The new head of Lions Gate Films decided he didn't want to risk losing money on it so instead of giving it the nationwide release it was promised, he dumped it, on opening weekend, to dollar/discount/budget theatres usually reserved for movies that have had their long run and are about to come out on DVD.
Another movie with a fresh idea, Trick R Treat has been in limbo since last year. Those who have seen it have given it glowing reviews as original and scary but the studios aren't willing to take a chance on it so it sits on a shelf where most people can't see it and all the while figures and costumes (found here!) for the movie are being sold to the public.
Hopefully we can get them to change their mind by finding some great original horror concepts to see in the theaters and by staying away from the remakes but who knows, they're the ones with the money and the fear.
-Rp