I don't like films with bad endings like Open Water (yeah, I know, it's based on a real event, I read the news). What's the point of wasting two hours on a struggle that ends bad? There's no payoff and certainly the path isn't the goal in a film where the path is extremely unpleasant.
An unhappy ending is as valid as a happy one, and often fits the story more. I'd kill to see the original ending of The Magnificent Ambersons
An unhappy ending is valid. It may even be MORE valid than a happy ending. But I don't like to leave a theater sad. I can watch the news for that and not pay extra.
I can be spoiled--do they off themselves, lose pressure and air, drift into the cold of space, or burn up on reentry. Cause I don't think rescue is on the list. Overall, I think this one is too sad for me to watch.