"What does it mean anymore to search for truth? It's so tired it's practically cliche: We think we know the difference between what's "real" and what's "fake," and we use those terms as if we've shored up a pretty precise definition between the two in our heads. Functionally, though, we operate as if we care less about what's "true," and more about what truth, however it's defined, does to affect our lives. We've transcended finding the difference; we now conceive of truth in terms of whether or not we have to take responsibility for it.
The best documentaries of the past 10 years, then, aren't about the gray area between truth and fiction, but about the responsibility of witnessing: When truth is in the eye of the beholder, what burden must that beholder carry? What is the burden of seeing?"
Note: This list has 31 films since I added The Act of Killing and The Look of Silence as different entries.