In its own right, it's a 10/10, no question.

However, when you consider how a single film such as the Matrix gets a two-hour documentary, then surely the Godfather films deserve something more than "A Look Inside". Of course, the one-hour-long "A Look Inside" is a very good documentary, but there is easily enough material for a major three hour documentary, catered for padrinophiles. Bear in mind that A Look Inside wasn't even retrospective completely - it was made before Part III came out.

That's my major gripe; with a bit of luck, when the Godfather Trilogy: 1901-1980, complete with all deleted scenes reinstated, is released, it'll be accompanied by the godfather (pun intended) of all film documentaries. And shooting scripts wouldn't go amiss. Something like the feature on Taxi Driver, where you can cut from a scene in the film to the script, and vice versa.