Rounding out the very bottom of AFI's list is Yankee Doodle Dandy, a grand bit of patriotism straight from the middle of the Second World War. James Cagney plays George M. Cohan, the legendary Broadway producer/playwright/composer/entertainer in a largely fictionalized account of his life.
For a first film to whet our tastes for this list, I will say that I got about what I expected. I knew from the release date (1942) and the subject that it would be sort of a fluff piece, and that's indeed what it was; as Samantha astutely observed, it lacked much of a definable plot. The film mostly proceeds from ancedote to anecdote, each one mostly serving to show off Cagney's dancing talent (yes, he could dance -- something you may not have known if you've only seen him in gangster movies) and the musical sequences. I think the film succeeds on this alone, though, as the musical numbers are fantastic and Cagney himself is a joy to watch.
I enjoyed the film. Of course, if it is a musical, I can generally be expected to enjoy it. And there is certainly nothing to disagree with about this one.