While I do like documentaries, the focus on popularity is perverse. And it's easily gamed by fake stars/collaborators , news puff pieces, and cheering crowds.
Two I liked a lot were 'get lamp' about adventure/infocom folks, and ... I can't remember the other name, but it was a documentary about Commodore.
Agreed - there's probably loads of interesting documentaries that could be made with people still alive. A movie on game consoles of the 60s and 70s would be great, imo. And there's probably some out there I don't know about.
There are plenty of computer things and people from the 70s and 80s which would make great documentary subjects.