In college I had to take 20th century US history twice, because I transferred. So I thought I knew enough about the Watergate scandal. But All the president’s men added much more to the bare facts I was familiar with. When you are studying history you are presented with a closed past, where beyond the raw data explanations are given by historians who piece their theories together based on the information available to them. Either way it is a static picture. But in the movies you see progression. In this case you could see how to journalists’ persistence managed to change history. It took much more though than their persistence. For example I admired their creativity, what tricks and ideas they used to squeeze out as much information from their–often unwilling–interviewees as they can. I would have given out much earlier.
It is not just the subject matter, an important segment of history that made this movie great. Sure, when real life is as interesting as fictional (or more) it makes good a story. But the screenwriters also did a good job in creating a script that balances historical accuracy with dramatic effects.
Real offices, editorial or otherwise, do not have music playing in the background. Much of the movie takes place in the offices where the journalist and their bosses worked. Therefore the lack of music in the movie–an unusual feature in modern cinema–helped to create a more natural feeling, a sense in the viewer that s/he is there in real space as history unfolds. Similarly, the two main actors, Dustin Hoffman and Robert Redford, didn’t over or underplay their roles, “just” made it as realistic as possible.
The difference between Oliver Stone’s historical movies and Alan Pakula’s that former wants to tell the whole story, while watching a movie by the latter, who directed this movie, you want to go forth and learn more about it. For example this movie did not follow in detail the whole story, just the first few weeks. The rest is told at the end in headline styles, coming from a typewriter. You need to do your won work to fill in the gaps, the movie can only show you cause and effect.
Thus I can recommend it to those who know something about the Watergate scandal, because it will show them the process how it enfolded. And I can recommend it tot those whose knowledge of the topic is limited, because it will teach them and hopefully intrigue them enough to educate themselves.