Here are ten of my favorites I have actually seen performed on stage:
Les Miserables
Wicked
Jekyll and Hyde
Cats
Phantom of the Opera
Chorus Line
Miss Saigon
Follies
The Mystery of Edwin Drood
The Will Rogers Follies
Ten favorites I have not seen on stage include lots of Rogers and Hammerstein:
The Sound of Music
South Pacific
The King and I
Oklahoma
West Side Story
My Fair Lady
Man of LaMancha
Jersey Boys
The Fantasticks
Newsies