imho -- some modern composers who should be recognized (pop/rock)

Using popular music forms should not be a barrier to recognition as a serious composer. After all, Chopin wrote mazurkas and Johann Strauss wrote waltzes -- the popular dance music of their time. And song cycles are likewise respectable, e.g. Schubert's "Die Winterreise' and Mahler's "Das Lied von der Erde." In such cases, the story (or poetic scene) is part of the art.

With that in mind, I would like to suggest a couple of 20th and 21st century "rock" composers for posterity to consider seriously (in addition to the obvious Lennon and McCartney and Harrison): The Moody Blues (actually several composers) and Janelle Monae. Listen carefully to The Days of Future Passed, or To Our Children's Children's Children, or Metropolis, or The ArchAndroid and you'll see what I mean.