"W. S. Gilbert once described Arthur Sullivan (13 May 1842 - 22 November 1900) as "incomparably the greatest English musician of the age." Besides contributing witty operatic parodies and a string of effervescent melodies to the Savoy operas, he wrote, amongst other works, cantatas, oratorios, concert overtures, incidental music to plays, numerous songs and a grand opera. He was the conductor of the Leeds Festival for almost twenty years, a friend of Royalty and a keen follower of the turf. He was knighted in 1883."
I have not heard a note of Sullivan's music, but know enough about music history to deem that he was an important operatic figure of the 19th century (and that he deserves a thread).