From my VHS recordings, here is the documentary "Comic Book Superheroes Unmasked", which aired on June 23rd, 2003 (with commercials included).

Commentary: This documentary was a reaction to the rise of superheroes films in the early 00's: With the success of the X-Men and Spider-Man films in 2000 and 2002 (and with 2003 promising the release of films about Daredevil, the Hulk, and the League of Extraordinary Gentlemen), this was the perfect moment to explore the history of the medium.

This was before the rise of the Marvel Cinematic Universe (with 2008's Iron Man) and before the revamp of DC Comics films (with "Batman Begins" in 2005), and so superhero movies were still a new (and uncertain) novelty of sorts, at this point.

This was before Stan Lee started having cameos in every Marvel film, before Joe Quesada became a celebrity appearing on late night talk shows to promote Marvel Comics, and before Frank Miller "went off the deep end" with comics like "All Star Batman" and "Batman vs. Osama Bin Ladin" (which ended up getting cancelled/rewritten). In comic book story terms, this was before crossovers and "Mega Events" completely took over Marvel and DC (which I believe started with "Avengers Disassembled" for Marvel in 2004, and "Infinite Crisis" for DC in 2005).

Besides being a good documentary on comic book superheroes, this also serves as a glimpse into what the History Channel was like in the Summer of 2003.