I also listed Airplane as one of my favorite movies, and it rips off most of the script for Zero Hour which is a terrible movie.
But Airplane! uses the material to do something new, Play it Again, Sam is an explicit homage/love letter to Casablanca. One works without having seen the source material just fine, and the other still works, but not as well.
Not really sure what to explain. They’re so different that I love them in completely different ways. It’s really just a coincidence that they are my two favorites. I don’t have to like Casablanca better just because Allan quotes it in Play It Again, Sam.
Fair enough, I guess. I was really just curious what those different ways were.