Back to the Future is the oldest kind of movie magic, a story both wild and innately familiar that's so confident it captivates the audience as a whole; it is that rare experience of sitting in a room full of hundreds of people, all feeling and thinking the same thing in unison. Seeing Back to the Future in a theater is proof that a great movie is both intensely personal-- the way I felt so desperate to time travel as a child--but universally appealing as well. Take anyone and everyone you know to see it, like I did, and get that unique thrill of discovering something you already thought you knew perfectly.
I saw the film tonight at AMC, which only screened it twice in celebration of the film's 25th anniversary. My favorite moment by far was towards the end of the film, when Doc flipped down those opaque sunglasses and says, "Roads? Where we're going we don't need....roads." The audience knew those lines by heart, recited them aloud, along with Christopher Lloyd, then spontaneously started applauding at the shared experience. What an awesome film.
[Also: Gawker has a nice list of 14 things from Back to the Future II that Actually Came True]