Horror is one of the most common genre of escape rooms, and although scary rooms can be great, I think it's an overused genre. There are some upsides to scary rooms, but there are also some downsides.
My opinion of scary rooms is largely influenced by the fact that I almost never think they're scary. Stephanie Noverraz says, "We've played some excellent, and also other pretty bad horror rooms, but what they had in common for me was that we had to stop playing for a minute and watch a show. And I actually prefer solving puzzles, even when the show is really well done and scary." There are many players who disagree with Stephanie, but I shouted a loud amen when I read her comment. I recently asked 350 escape room enthusiasts if they prefer scary rooms or rooms that aren't scary, and 74% (259) of them said they prefer rooms that are not scary. Why then do scary rooms seem to dominate the escape room world?
But the problem isn't really that designers use scary themes such as zombies, kidnappings, murders, nightmares, etc. Those genres are fine and often great, but they can't get so caught up in the uphill battle of scaring every player that they forget to immerse them with challenging and engaging puzzles.
Scare is an overused gimmick. The thrill of competition is enough to keep my excitement level high, and attempting to scare me only distracts from the tool that is working. I don't get scared; I get annoyed. This is one of the reason why I think The Escape Game's rooms are so good. They know their niche, and they focus on perfecting it.
There are some people who don't like scary escape rooms for the opposite reason. Those people are often easily scared, and they don't like it. They don't like horror rooms because they don't like to be scared.
With that said, I have played some very good scary rooms. The Cabin at Escape Hour in Gig Harbor, Washington comes to mind. It's a great room with a quality storyline, real puzzles, and excellent design, but even in that room, I felt annoyed when the scary moments happened. My brother and escape room teammate (Billy) disagrees with me. He loved that room, scares and all.
Horror or Thriller
The biggest difference between horror and thriller is in the names. The primary objective of a horror is to horrify, disgust, or scare the audience. A thriller can provide a thrill by scarring, but it can also accomplish a thrill with a chase, a mystery, or any other intense plot.
In horrors, the main villain is known and feared. In thrillers, a lot of the thrill comes from not knowing who the villain is.
Horrors usually have victorious or happy endings. Thrillers often have sad endings. I guess you could say that a scary room that you escape is a horror, but a scary room that you don't escape is a thriller.
You could make the argument that scary rooms are thrillers because one major difference between a horror and a thriller is that thrillers are unpredictable, but horrors are usually very predictable. Escape rooms can be predictable or unpredictable.