Do All Great Stories Begin (or End) With Tragedy?

[Gildarts]

The mods can move this topic if they want, but me, Vic, and Cat were brainstorming about at what point a story begins. Most stories, when I look back, have kind of a sad beginning, probably as a device to keep us, the readers, reading. We want to experience the completeness that the end gives us and a purposeful beginning.

So I ask, do all great stories begin with tragedy?

Examples: Supernatural, Harry Potter, and well, I'm sure this list could go on for a while and I'm a bit lazy so...