Back to the Future is a really great film because it has everything you could ever want in a movie, in perfect balance. It's a time-travel/friendship and family drama story mixed with a whole of comedy, and there's even a musical number (that doesn't even suck). And what I think is most interesting about the film is how when you watch it as a kid, it is basically dazzling because "like woah, he traveled through time" but when you watch it as a pseudo-adult there are many more deeper themes to pick upon.
I would be totally remiss if I didn't talk about the score of this movie, which is easily in my opinion one of the top 10 best scores for a film ever. The melody line is unforgettable and powerful and heart pumping if ever an action movie score was. Ku-Dos.
Also for what it is worth, all of my adult opinions on time travel come from this film. And time travel is totally possible in certain conditions. Not that I would know about it though.
And let the official count show also that this is the second Robert Zemeckis movie I've picked on the countdown. I suppose we shall see if that sub-list grows.
Doc Brown: So tell me future boy, who is President in the year 1985?
Marty: Ronald Reagan
Doc Brown: Ronald Reagan the Actor? Who's vive President, Jerry Lewis?
Rumor has it when Reagan watched this at the White House theatre he made the prompter rewind the film again so he could list to the dig once more. And then laughed his head off. He may have been a crazy right-winger but at least he had a sense of humor.