The Right Stuff with Apollo 13 a very close second place.
Isn't it sad that of all the momentous events of history that been the subject of movies there hasn't been even one "big time" movie solely dedicated to Apollo 11 and mans first landing on another celestial object? I guess the upcoming movie on Armstrong's life will sort of serve the purpose.
The problem with Apollo 11 is that it lacks drama in the movie sense - there's no mileage in an almost flawless success story. Don't get your hopes up too high on the Armstrong biopic - Hollywood is likely to turn that into slush. Would they ever be able to capture Armstrong's weird anti-charisma?