Astaire movies have great charm, but would not rate particularly high on my list, as other musicals have _better_ songs (my opinion) and were written as coherent works. Astaire musicals, and I may be wrong, used the best songs from otherwise unremarkable Broadway musicals.

As for the South Park movie, I can take it or leave it, though Uncle F*cka and It's Easy Mmmkay are notable masterpieces.