Gone With the Wind, 1939
Well, by the time about 7:45 rolled around, I had a burger on a plate and some fries, and a drink. Settling down on my basement sofa, I flipped to TCM and waited for the film to start. From the opening music, I was hooked. For the next four hours I didn't move off my sofa, except to run to the freezer quickly to cram another creamsicle. I eventually polished off the whole box by the end of the movie.
Gone With the Wind was my first foray into the epic film. It also taught me not to finish a drink within the first twenty minutes of the film, because you're not going to be leaving the sofa for another three hours. It also introduced me to Vivien Leigh, who has since become my favorite actress and one of my favorite people. It was also the first Clark Gable film I saw, and I kind of went "Oh. So THAT's Clark Gable. I get it now, his appeal."
I think you really need to see Gone With the Wind if you are really into films. There's really amazing performances, I think the cinematography is brilliant, the score is beautiful, and it's a prime example of the Hollywood epic that they just can't make anymore. And I think that it's pretty safe to say that it's the most famous film of all time.
PS: Even when you adjust for inflation/deflation, when you add up all the numbers, Gone With the Wind is still the highest grossing film of all time. Take that, Avatar!