I agree to an extent. I will say up-front that I utterly loathe torture-porn movies (a few of which I’ve been obliged to watch thanks to my job as a subtitler) for the simple reason that I find gratuitous and deliberate cruelty utterly reprehensible, and the one action I cannot forgive. I admit I cannot understand why anyone would enjoy it, except to consider, intellectually, that they are experiencing an extreme sense of schadenfreude - which may in itself have some evolutionary grounding, in the sense that to see another’s misfortune is to know that you are better off than they are, and more likely to survive.
Having said that, I have seen a couple of similarly-themed movies in the cinema (the first Saw and Wolf Creek) and I think there is just a bit more to them than gratuitous violence and gore (although this is undoubtedly a drawcard for the less reflective amongst our fellows). Yes, there is the straightforward thrill aspect. However, with Saw, for example, there is also the nagging internal interrogation - what would I do if I were in the victim’s place in any of the ‘games’? This is certainly not a comfortable speculation, and I think some people like to test themselves by proxy, without any of the immediate physical risks faced by the characters in the movie.
I don’t think the idea of the battle between good and evil is entirely lost in such films, either - although it can certainly be obscured by the bloodthirsty nature of them. Something I found in Wolf Creek, for example - and also Sean of the Dead, which, if you haven’t seen, I recommend - was a portrayal of the sheer mundanity of evil, and how it isn’t necessarily the seductive, dark-cloaked predator hidden in the shadows, with an elaborate plan to bring about your destruction in various exotic ways; no, it could just as easily lurk in your next-door neighbour, or the unassuming stranger who welcomes you to his house on on a cold, rainy night.
Maybe there is survival value - and thus a deep evolutionary connection - in the notion that we can’t take anything for granted, that we should be wary of completely letting down our guard.