I agree with some of your points, but I personally would put "A Chorus Line" in the top ten of any list of Best Shows. It may be the single greatest example of a fully integrated musical musical ever created -- great book, great score, great staging, great design, great choreography seemlessly blended into a unified whole. Twenty fully-dimensional characters in a script rich with humor, drama and pathos, requiring a stage full of true triple threats (especially the original Broadway incarnation of the show), it's one of the finest examples of everything that the musical theatre can be.
I also think Showboat still retains much of its power and brilliance 77 years later. It's truly a credit to the work that the last revival roughly a decade ago, still so resonated and spoke to contemporary audiences that it ran nearly a 1000 performances -- the most successful production ever mounted of the show on Broadway (it ran a year longer than the landmark original production).
"amazing book, amazing score, and something that when you walk out the door of the theatre, you something inside of you has changed; a show that has the ability to totally suck you into its world and forget the outside...."
I would say that Showboat, Oklahoma and A Chorus Line have all of those qualities and more in spades....
"What a story........ everything but the bloodhounds snappin' at her rear end." -- Birdie
[http://margochanning.broadwayworld.com/]
"The Devil Be Hittin' Me" -- Whitney