What makes Cabin in the Woods so successful? Part of it is the genre-knowingness: we see zombies and semi-torture porn areas and cenobite-knock-offs and everything else we've come to recognize as horror movies (minus maybe the non- or semi-supernatural slasher). The film also explains lots of things that have become genre standard: for instance, the group splits up because the white collar puppeteers expose them to some dumbness gas; and Dana drops the weapon she was just using because the handle gives her a little shock. Those are two things that happen all the time, the kind of thing that audience members yell at the screen about; so here we get the trope but we also get a cute explanation of the trope.
I've also seen some argument that the film plays with character. So a typical horror film might include pretty flat stereotypes--jock, slut, egghead, virgin. But these characters start out more complex: Curt is a big guy, but he's funny and smart--only later does his personality get flattened to "have sex, do violence" and that semi-ridiculous speech before he attempts to jump the gap. Also at the beginning we learn that Dana, far from being a virgin, has actually just been broken up with by her lover, who was also her teacher. So we could say that Cabin plays with its genre even here, giving us what we expect (the flat characters) but also explaining that flatness or showing how the characters aren't flat.
But I think we have to look at the structure still. I think I need a new blogpost for that.