I think my all time favorite documentary is Kevin Brownlow "Hollywood". I hope that it some day comes out on DVD. If I had to list the number of documentaries I love it would take forever. My main collection is mostly documentaries. There is a terrific documentary about the life of Olive Thomas that is available on DVD which I encourage everyone to see. The Louise Brooks docu that was shown on TCM some years ago was also fantastic-Based mostly on Barry Paris's book. I have a boxed set about Keystone that I am very fond of as well. It shows a lot of clips but has a very good underscore commenting on the different actors and actresses, shorts, ect. It's in a metal case and I have only seen it for sale once. Purely for educational purposes and really the quality is above average.
I wish that someone would make a good documentary about the Pickfords. Not just Mary, but Jack, Charlotte and Lottie's life and why Jack and Lottie died young. It would make an interesting bio in the respect that Charlotte was probably one of the keenest, sharpest agents that ever walked the pavement in Hollywood. That woman was way way way ahead of her time--she could intimidate Louis Mayer. I have played with the idea of a screenplay called "The Pickfords" but I doubt there is much interest to make it anything near marketable for this day and age. Anothe thing I would love to see is just a documentary about costuming.