Who is the greatest musical theatre composer of all time?

While art is subjective, there are a few luminary composers who have made significant contributions to musical theatre and whose work has stood the test of time. One could make a case for any of the following. Jerome Kern wrote more than 700 songs and wrote the music to "Showboat", one of the first Broadway musicals with a serious plot and themes. The songwriting team of Rogers & Hammerstein was the first to use songs to further the plot vs. break the plot for a song and dance. Their musicals are still enormously popular and performed constantly. They include "Oklahoma", "The King & I", and "The Sound of Music". Leonard Bernstein, while most known for classical music made a major contribution to musicals with the groundbreaking "West Side Story", an updated Romeo and Juliet story with spectacular music, every song a classic. Bernstein collaborated with Stephen Sondheim on this musical. Sondheim ushered in the modern-day musical in which shows might explore a theme vs. a linear plot. While he is often criticized for not having "hummable" melodies, his genius is undeniable, and he did have one bonafide hit with "Send in the Clowns". Jules Styne composed what is often considered the greatest musical of all time, "Gypsy". The dynamite songwriting team of John Kander and Fred Ebb composed the longest-running American musical, "Chicago" and the dark yet entertaining "Cabaret". Finally, while often criticized by musical-theatre purists as blatantly commercial, the success of Andrew Lloyd Webber cannot be denied. He composed the enormously successful "Cats", the longest-running Broadway musical of all time "Phantom of the Opera" and even into his 80's is still composing, with the recently opened "Bad Cinderella" on Broadway.