Why do we like some films and novels, but not others?

"Casablanca is one of the most loved films of all time. Why is this? Once again, it seems to have to do with right and wrong. The first part of the film depicts people's attempts to flee the Nazis in Europe during the Second World War, by making for Casablanca from where they can leave for Lisbon, from where passages are still available to America. Then the film is taken up with a moving love story between Rick (Humphrey Bogart) and Ilsa (Ingrid Bergman). In the film's single long flashback, we see them happy in Paris before it's over-run by the Nazis, having told each other they wouldn't ask about their previous lives. Ilsa fails to keep an appointment with Rick, to leave Paris with him by train, but now, in Casablanca, she appears with a husband, the freedom fighter, Victor Laszlo (Paul Henried). If Casablanca is a film you love, you will know that rather than resonate with the usual Hollywood fantasy that love conquers all, in which Rick and Ilsa would leave for Lisbon and go to live happily ever after in Illinois or Nebraska, Rick arranges for Ilsa to leave with her husband. He does the right thing. The reason we like the film is that it resonates with our belief, embedded in a deep and important fantasy which perhaps can motivate our lives, that doing the right thing is the right thing to do."
By Keith Oatley