Happily Ever After

I once had a teacher who claimed there was no such thing as a happy ending in “great” literature. By great, I can only assume she meant those classic novels which are still taught and/or have been revered and loved throughout history (The Great Gatsby, Moby Dick, The Catcher in the Rye, The Grapes of Wrath, etc).
This brings me to my question of the day – What is the best novel with a happy ending? As in, truly, 100% happy. (I have a thesis-like response at the ready for anyone who says Pride and Prejudice!)

In the way that most “great” writers are tainted by pain, loss, or addiction, do novels need to suffer the same fate in order to be respected?