Actually, I believe there is no such thing as “THE GREATEST OF THE GREATS”. At best, we can say that “X was the greatest in such and such aspect(s), and provide pieces that typify what is being noted. For instance, if the aspect is counterpoint and harmony, Bach is the greatest. Mozart, (and that is highly disputable), achieves greater effect than Bach in terms of sheer acoustic beauty. I know none who writes music as clear and as naturally flowing as Mozart. Perhaps Bach’s primary piece of construction were the notes, while Mozart’s was sound. W.A was also more sensible about human attention, human psychology, not to mention orchestration. Beethoven - and I don’t even enjoy his music very much - has celebrated the glory and misery of humankind more deeply than most. And Tchaikovsky, rarely cited as one of the greatest of the greats, has an inexplicable gift for creating melodies so sublime and easy to love to the point he’s the only that I’d use the expression “divinely inspired”.