Oh, my. Where to begin? I love musicals. I am old, so they are all old musicals, of course. They have a lot of cultural context and might be hard to understand outside the U.S. "The Sound of Music" is a great musical, AND a great movie version. And it is not set in the U.S. and not as U.S.-centered as others. I think "Show Boat" may be THE greatest musical of all time, and touches on serious themes. All the songs in it are fantastic. You should be able to find clips on Youtube. Paul Robeson sings "Old Man River" in 1936: https://www.youtube.com/watch?v=eh9WayN7R-s And Helen Morgan singing "Just My Bill" https://www.youtube.com/watch?v=3HeasqkO1Ko For at least a semi-modern musical, I love "Ragtime."

As to WHY I like them, a good part of it is the literate lyrics and clever rhymes of the songs.