When creating a story who are you really writing it for? You? Your mother? The little old lady that lives at the end of the street who always smells of cats? It's easy enough to write something that the writer's passionate about, but will the reader feel the same way? After all, with the hope of getting that story into publication, isn't the real person you're writing the story for going to be the reader?
But how do you know what the reader wants? Take a trip to the book store, see what people are reading (not just the type of story... cough, vampire, cough), what characters draw people in? Does the reader like intricate plots that keeps them guessing from beginning to end?
It's not that easy to identify what people want, especially in the terms of novels. There's only one way to know what readers want, and that's to become a reader yourself. If you know what you like or don't like and see how published writer's put things, then chances are that you've already discovered what they want.