Absolutely, they must be included as should Durufle, Olivier Messiaen, Saint-Saenz, Gigout, Henri Mulet, Guilmant, Lefebure-Wely, and Leguay. Also Pachelbel William Bryce, John Stanley. And, also Franz Liszt composed some beautiful, yet difficult, organ compositions. His "Prelude and Fugue on BACH" is absolutely breathtaking.Buxtehude, Mendelssohn, Franck, Reger, Jongen, Schmidt.
EDIT: and if you want to dive into French organ music, the already mentioned Alain, Widor, Vierne, Dupre, Langlais, for starters..