Scott at 2015-10-26 14:48:37:
I'll kick off things with this observation. Joel Coen has been quoted as saying this: “Every movie ever made is an attempt to remake ‘The Wizard of Oz.'”
That is true of Back to the Future.
Think about it. What is Dorothy's problem? At its root, she doesn't feel like her home is a home. A big part of that is she feels so different than everyone around her. They're all adults, she's a child. They all have jobs / a function on the farm, she doesn't and gets into trouble. She even DRESSES differently than her aunt, uncle, and the three farmhands Zeke, Hickory, and Hunk. And there's this: She's an orphan.
Marty McFly, I would argue, is very much in the same boat: He doesn't feel like his home is a home. His mother, father, sister, brother, uncle, none of them have the same interests or 'cool' factor Marty does.
So what happens to each? Both Dorothy and Marty get transported through bizarre means to a different world: Dorothy to Oz, Marty to a time decades ago.
They both learn a similar lesson, however whereas Dorothy comes back and accepts the Kansas farm as it is as her home, Marty returns to find his family has somehow turned out to be great, an idealized version of what he might have dreamed of in the first place.
I think the difference here is tethered in part to the eras in which the movies were made. The Wizard of Oz was produced in 1939, as the U.S. was slowly recovering from the Great Depression, so the message there -- be happy with what you have -- probably resonated with most Americans as they struggled to survive with their meager incomes and lifestyle.
BTTF, on the other hand, was produced 1985, right in the middle of the Reagan era where the message was, "It's morning in America." Feel good about things! Feel good about yourself! So Marty returns to a classic wish fulfillment scenario fitting the upbeat posturing of the political and media powers that be.
Bottom line, both Dorothy and Marty go on a classic Hero's Journey:
Separation. Initiation. Return. Both Protagonists come back transformed by the experience, but in BTTF the transformation is more about how Marty's 'interference' in the past has changed the present.