(and the earlier movie The Cave
) were both rip-offs of the ideas on the book by Jeff Long of the same title which was much more horrifying.
The setting is the same - caves. So is the title. I suggest reading the book and see for yourselves.http://www.amazon.com/Descent-Jeff-Long/dp/051513175X
As for me, I've never liked watching horror movies. Because of the gore. I'm very squeamish of open wounds so I like the more psychological/mindfuck horror ones, not the ones with lots of blood and nothing else. I tend to stick to books though. Stephen King, Dean Koontz, and Robert McCammon are my favorites in that genre. However here are movies I liked (The Exorcist was already mentioned):
(Not exactly horror but I loved both of them and they got more gore than most horror films
):Grindhouse Double Feature (Planet Terror & Death Proof)
(Not exactly a film, but a video game)The Suffering
And lastly... the Japanese and Koreans make the most terrifying psychological horror movies ever. I like this one better than The Ring.Ju-on (The Grudge)