Though now that I think about it, I reckon almost any story can have a happy ending or a sad ending, depending on where you say "The End."
Pretty much every romance novel (at least, in the Christian market) has a happy ending. But much of the story (at least most the good ones) aren't necessarily happy throughout. For an example, I'll use Beauty and the Beast because everyone always seems to choose Cinderella lately.
Spoiler alert for the Disney version if you skipped the years 1991 through the present, or maybe if you don't like cartoons and haven't had kids in your life!
So imagine the story ended when Gaston stabbed the Beast. Story instantly becomes a tragedy, for lack of a few minutes of storytelling. In the alternative, what if it ended 50+ years in the future? OK, so they say "happily ever after," but if they were real people they surely experienced some disappointment or heartbreak. Belle's dear father had to pass away at some point, never mind Belle and the Beast's eventual fates.
Also, you could tell a story about the same characters but in a different timeframe, and have something completely different. What if it started when Belle's mother met her father Maurice? At some point Belle's mother presumably died (or otherwise left the picture)--what if the story ended there? Or what if the story ended with Belle and her father finally coming to a new town where they were, if not accepted, at least tolerated? OK, yes, I'm sure there have been countless fanfictions writing about Belle's early life (and the Beast's!) but still. There's a story there.
In my opinion good fiction figures out exactly where to
OK, ironically (?), Blogger uploaded this before I meant it to! LOL. Though I guess the above is a good lesson--you have to know exactly when to end the story to match with your beliefs, and (unless you're trying to turn the audience for a loop) the expectations of your audience as well. An optimist and/or someone writing for an audience that expects happy endings will end with a happy ending. Few people who want their stories to be enjoyed end with a completely unhappy ending, no matter how dark the story. Myself, I figure, why not end with something happy?
My favorite happy endings are the "deliriously happy" endings like the Disney films Bolt and Princess and the Frog, where everything ends up just unbelievably happy for the characters. If you're still here, how about you?