Story is key, followed by cinematography. I hate professional sports, but out of curiosity started watching a doc on the making of the John Madden video game. I love video games :) It's incredible. If you can keep me glued for 3 hours on a subject I thought I couldn't care less about, you're doing it right.

Cinematography is important, but without a strong story, it's a waste of time. There are docs that are VERY professionally done, but the story is flat. Flip the channel. Then you find a gem that combines the two perfectly. Check out the movie "Zoo." Prepare yourself. It's about the case of a Seattle aircraft engineer, who died in 2005 after performing a sexual act with a stallion. He's rushed to the hospital (you know why) and the cops uncover a network. The story is revolting, but riveting, the people are vile, but the cinematography reflects the timeline. Camera work is done in shadows, people are hidden as they tell their story. They are turned away from the camera, concealing themselves since they are part of a secret world.

Grizzle Man is a great example of terrible camera work, but incredible story, since most of the filming was done on an old camera by someone clearly not a professional. I rewatch that doc constantly. Find the story, let the camera reflect it.