Hm, I disagree. Usually when you read a book/watch a movie, you do have a pretty good idea who will survive. I mean, even in the original trilogy, most people knew how things would go down since the books were well known. I would say more interesting is how it goes down, and you can still have tension even if you know the final outcome. Same thing with folk tales: you know the hero is going to win, but it is still enjoyable to hear the tale told.