I've been watching Metal Evolution. It's an 11 episode documentary on metal by Sam Dunn of Victoria B.C. (He's the Anthropologist who made the Metal: A headbanger's Journey and World Metal Docs as well as Iron Maiden: Flight 666)
I find this doc is superior to the other two, just because it's 11 hours of content allowing for much more detail.
Really great stuff in the Progressive Metal, Grunge, pre-metal and other episodes.
Unfortunately they didn't get to do an Extreme Metal Episode which covers Death Metal, Grindecore, Black Metal etc, but there is a fundraiser to get that started: http://www.youtube.com/watch?v=7Dhm6UtnuKs
It's also lacking Doom/Stoner Metal which sucks. I think they could do an entire episode on Doom Metal.