Fictional Character Theory
Fictional characters aren't exactly like real people. For one thing, they are simpler than real people. This is largely because when we look at a real person, we seldom see her "being herself." Instead we see the image of herself that she projects. But when we look at a fictional character, we usually see her true self. We get into her head.
Also, our view of a real person is almost always distorted by prejudice. It's colored by the impressions left by what people have said of her. It heavily depends on her reputation, which may or may not be appropriate. It's biased by many things, such as her status with respect to us. None of these influences blur or shape our view of a fictional character.
At any given time, a real person plays a part in multiple stories. These include the story of her life at home, at work, and with her friends. These stories overlap. This confusion of plots and influences complicates every choice, making it difficult to sort out a real person's actions. Also, real people often compartmentalize, adapting their projected image to the environment like chameleons. All too often this results in stunning logical contradictions in their belief system, situational ethics, and inconsistent behavior. Indeed, Adam invented political correctness by eating the apple just to agree with Eve! Most people do this twenty times a day. They behave like weather vanes to avoid conflict. (Good fiction is blessed break from that.) So, real people are often "complex," well-nigh impossible to figure out.
We love fiction because fictional characters are possible to figure out! Because they engage in conflict. In fiction we see the real person, not her image. In fiction no irrelevant aspects of character cloud the picture. In fiction no false information or self interest warps our view. In fiction one story at a time is told. So fictional characters are simpler and more sharply defined than real people. They are the distilled essence of real persons.
We see who they are through their actions.