In Orson Scott Card's book How to Write Fantasy and Science Fiction, he explains something he calls the M.I.C.E. quotient. M.I.C.E. is a way of finding the focus of a story. It stands for Milieu / Idea / Character / Event.
Card says that every story will fall into one of these categories. A story can be rewritten so that it falls into a different category, although it retains its plot and characters, but it will rarely be worth reading afterwards. A whodunnit is an exemplary idea story: the entire story focuses on answering a question; on finding the big idea. If a whodunnit was rewritten so that we knew all along who did it, but focused on character development, it would be pretty boring.
In my case, I think it would be more appropriate to use a m.i.C.e. quotient. Whenever I read (or write), my focus is on the characters. If I read a murder mystery, I am usually at least as interested in the murderer's psychological motivation and the why the detective cares about solving the case as I am in the solution to the mystery.
If the hero needs to save the world, I tend to see the big event as a means of character development, rather than the point of the story. I'm a little better about milieu, but I still tend to think of it as secondary to character, even in a book like Gulliver's Travels. When I'm reading, this probably means that I don't get everything I could out of most books, but it's not really a big deal.
When I attempt to write fiction, it's more of an issue. I conceptualise a really great story, except that it doesn't have a plot. I will not notice that until I actually try to write it down. Then I realise I have nothing to write. I may have a fascinating set of characters who will interact believably, but if they don't have anything to do, nobody will care. If they don't have a background, the story will be rather dull. (I'm not quite sure about Idea, though.)
It's taken me a while to figure out the roots of what I struggle with when writing fiction, but the M.I.C.E. quotient was a very useful tool. I'm surprised that I haven't seen similar concepts more often.