Who-done-it? This is such a cliché there is even a genre named after it. But does it really matter who did it? I mean, is a novel/film less interesting when one knows who did it ahead of time?
This is not the case for me. As a writer, I enjoy a good story just as much whether knowing or not who did it, i.e. the denouement or ending.
In fact, every time I come across an awesome story, I make it a point of reading/watching it again, and I enjoy the insight I have gained on the characters and I sympathize for them who do not know what is going to happen to them.
If the story is good, and the characters solid, knowing the ending does not alter the enjoyment of the experience the book/film offers - the ability to transport the audience into a fictional reality - which is what matters to me and, I think, to a lot of people who enjoy watching their favourite films over and over again.
But where did this topic come from? Well, friends and acquaintances often will recommend me a film they really enjoyed. When I ask them what it is about, often they will say, "Oh, I can't tell you without giving away the ending." But the fact is that I have a busy schedule and, unless I can be guaranteed a good denouement/ending, chances are that I am not going to bother going out of my way to sit down and read said book or watch said film.
If, on the other hand, the plot actually is interesting to its end, I will make it a point to read this book or watch this film, comfortable in the fact that I know there is a good denouement at the end of it, and that I have not just wasted 800 pages or 2 hours on a book or film which sucks.
Furthermore, when writing, I always come up with the ending first and work my way towards the beginning from there. I don't know. Maybe it is just the way I am wired. But still, I guess that what I am saying is that a good story is a good story, whether the ending has been previously disclosed or not. And, in contrast, a bad story is a bad story no matter how the creator/audience try to hide its ending.
Because, if the story is boring, it does not really matter who-done-it. The only thing that matters then, is when-is-this-over?