Similarly effective horror films?
The endless parade of comedies, comedies in disguise (slashers et al), torture-a-tourist films, ghost movies, zombie movies, remakes, and other such similar fare in the genre gets really tiring to the point where you wonder why you even bother anymore.
Then - you stumble onto something special, like In A Glass Cage, which deals with truly horrific material in an exquisite, deeply felt way. It's so incredible but so dark and difficult I'm not sure I'd watch it again let alone recommend it to someone else, but such is what horror SHOULD be, to be perfectly honest.
Can anyone recommend something like that? Something legitimately dark and disturbing, but because of the horrible truths and real emotions it contains and not because of the kind of childish bloodletting you'd find in a faux-snuff film. Although, gore itself is fine and not the problem here, because the only other film I can think of that similarly stuck with me was Martyrs (2008) which has a crucial emotional component which complements and intensifies the portrayal of the violence, hence the reason it is affecting.
(For the record, I did not much like Requiem for a Dream, Salo, and Irreversible, as I found the first over-the-top, the second lacking in empathy and excessive in sleaze with pretentions to art, and the third schematic and tedious. All three rather shallow. To pick a couple random well-known 'extreme', 'disturbing' films out of a hat.)
High goals and tall orders. Heeelp me!
http://www.youtube.com/watch?v=kqYDRxdgnC0