I'm not expert in the movie business, but it seems like writers don't have much control. I know I'm only thinking feature films, here, but it seems like the producers and directors have their visions realized. You see the promotions and they're like, "From Executive Producer, This Guy. Directed by That Guy. Starring, These Two." And if those names are big enough, they might not even bother telling you what the story's about.
If you write a story, you visualize everything all in your head. In your mind, you know what the characters look, what their voices sound like, what the environments look like - every single detail. When you write a book, you have to surrender a lot of that to the reader. You know that the readers will build many those things in their own minds, with their imaginations. In film, visuals and sounds are created beforehand. Rooms are rooms, people are people. No more descriptions, show them what you want them to see! I think that's an amazing opportunity for a writer. At least, it sounds like Christmas to me.
But if you hand (read: sell) that script to a producer, it's his movie. He'll choose the director who's gonna shoot things the way he thinks it should be seen. He'll read that script and visualize things his own way. Producers, directors and actors are what drive people to the theaters because they're what's recognizable.
Take a director with a signature style, like Tim Burton. I don't know how anyone could ever hire that guy. I'm not saying his movies are bad, but I can't imagine how the tiniest sliver of anyone else's vision could survive! Every film he directs becomes his. That's going to happen with any director, though to a lesser degree. It has to. He's not the writer.
|Robert De Niro, as himself.|
Let's not forget about sex, violence and comedy. Unless you're James Cameron, you've gotta excel in at least one (probably two) of those areas to make bank at the box office.
I just don't think I could ever hand over a script without being in charge. But how often is the writer also the producer and director of a feature film? It's not too often that one person is given that much power.
I guess if you wrote a screenplay and you felt like me, you'd either have to shoot it yourself, or make good friends with the director. It's probably good that I won't be in those shoes.