Since his seminal work, 1990's "The Civil War," I have tried to make a point of watching each subsequent documentary made by him. While I thought that "The Civil War" was transcendently great, I must admit that I have been underwhelmed by some of his subsequent efforts, including the high profile "Baseball" (1994) and "Jazz" (2001).
The first episode of "The National Parks" started slowly, I thought, and I almost gave up on it, thinking it was another effort like his 1999 documentary on Susan B. Anthony. But I hung on a little longer, in part because the topic intrigued me, and in part because some of Ken Burns' past work has been so great. And I have been very glad that I did. This is his best work in many years, I think.
If you missed it when it first aired last week, you can watch every episode of "The National Parks" for free on PBS.org.