Should all stories have a happy ending?

I was watching an episode the other day from the show Beverly Hills 90210 Season 3 Episode 16(It's A Totally Happening Life). This episode was about two guardian angels that foresee a truck colliding with the gang from 90210. The 90210 characters were on a school bus on their way to visit children in order to deliver them Christmas gifts. To sum it up, the truck collides with the bus and miraculously the bus had no scratch on it. Also, not one person was hurt. It was implied that they were saved by a higher power. Although this was a nice way to end the show, it was very unrealistic. In my opinion, the writing was awful in that episode. As a writer, I actually appreciate it when something ends accurately that depicts real life situations. Could a bus collide with another truck and realistically would everyone be alright? Other shows have been realistic. On the OC, the writers killed off a crucial, main character. They could have chosen the character, Marissa Cooper to leave the show differently, but they took a risk and were realistic about it. Look at the classic movie, Gone With The Wind. Did that movie have a happily ever after ending? No, not really. I had a conversation with a friend about this and she said that although it is nice to have a happy ending, it is sometimes unrealistic and can appear too perfect. I am definitely not saying that we can't have a story where everyone does live happily ever after. As the reader, we root for that and hope the main character is on top. However, it also does not hurt for the writer to take a chance and end something differently from what the reader expects. Don't be afraid to take risks as a writer. It only makes the story more compelling. As I am writing my blog, I am thinking about my own book that will be published soon titled, Ignition. I can only hope that my reader is surprised and affected by the ending in my story. "If you are willing to risk the unusual, you will have to settle for the ordinary."(Jim Rohn) "I'm a writer, adventurer, and risk taker on a quest to join the top 1% of the world."(Tyler Tervooren)