Sitting in the pit orchestra, my favorites are Miss Saigon and Les Miserable. While some may say Les Mis is trash, I loved playing the music. We had an amazing cast so that may have helped.
I also liked A Little Night Music because I got to play the alto flute as well as flute and pic.
Least favorite to play were any Andrew Lloyd Webber scores. Once you've played one you've basically played them all.
Yes, I judge musicals and operas on actually performing the scores, not necessarily the story or the overall music. Feel free to judge me on that.