The ending is the last emotional high that an audience feels right before the story ends. Thus it’s important that your ending not only peaks the audience’s emotions, but also makes sense in relation to the rest of your story.
Pick a great movie and the ending is almost always memorable. In “Star Wars,” it’s the Death Star blowing up. In “Casablanca,” it’s Rick walking off with his new comrade saying “This could be the beginning of a beautiful relationship.” In “It’s a Wonderful Life,” it’s Jimmy Stewart hugging his family as friends pour in with the money he needs.
All of these endings are both emotionally satisfying and thematically satisfying to their particular story. What if we switch endings? Instead of Luke blowing up the Death Star, let’s say the Death Star simply misfires and jams, then Luke flies back to the rebel base and everyone hugs each other. Would that be satisfying?
What if Jimmy Stewart in “It’s a Wonderful Life” has to face the bank auditors alone with no money and suddenly Jimmy Stewart pulls out a gun and blows the bank auditors away. Would that be satisfying? It’s not the scene itself that makes the ending satisfying, but its link to the rest of your story.
Every good story has a theme and your whole story sets out to “prove” this theme In “Jurassic Park,” the theme is that man shouldn’t mess around with nature. All throughout the story we can see the consequences as things fall apart. Yet the ending is slightly unsatisfying because the T-Rex arrives and saves the day by eating the Velociraptors.
Huh? While visually it’s cool to see dinosaurs fighting, it smells of a “deus ex machina” ending where something out of the blue saves the heroes. In this case it’s a giant T-Rex that appears out of the blue despite being huge and noisy, thus weakening the ending.
In “Raiders of the Lost Ark,” Indiana Jones fights the Nazis every step of the way, yet in the end defeats the Nazis when Indiana Jones simply closes his eyes. Once again we get a cool visual scene of spirits floating around, killing Nazis, but the movie set up the whole Indiana Jones vs. the Nazis idea, and he doesn’t do it.
In “Inglorious Basterds,” the Jew Hunter massacres the Jewish girl’s family in the beginning of the story, so we expect to see those two clash at the end, but we don’t.
These endings of movies weren’t awful, just not as unified thematically as they could have been. A good ending cements your story in the mind of your audience. A bad ending disappoints, while a murky ending like in “Jurassic Park” or “Inglorious Basterds” can leave some people happy while others dissatisfied for some unknown reason, and that reason is that the ending wasn’t unified with the theme of the rest of the story.
You can have a less than stellar ending, but why do that when you can just shoot for a great ending that supports your main idea or theme?