Here are my current thoughts, which I plan to include in my essay. Any comments/ideas are more than welcome.
An ending must satisfy both the action plot and the emotional plot of the story. We must know what happens in the most basic sense (does he get the girl? do they make it home alive?) and also what happens emotionally to the character that changes him/her in whatever small or large way.
Studying a good ending is really like studying the whole story because the ending must be set up in so many different ways, starting with the title. Everything in the story, every character, every action, every symbol must lead to or point to the ending.