Who knows, I think mainstream american audiences just want to see happier upbeat films these days. They don't want a movie they leave feeling down or disturbed by. And a lot of the reason Coraline grossed as much as it did was because it was in 3D theaters and 3D tickets are expensive as hell. That's not saying it was a hit only because of that, but it would have easily made 20-25 million less if in 2D and that's if people would still see it without the 3D gimmick. Look at My Bloody Valentine 3D, that film grossed 55 million. Without being in 3D that film would have been lucky to make 15 million.