Time to get rid of the dust on this thread........
Greatest rock band...humm......I will go with Led Zeppelin for various reasons. Not only the influence they had on future artists, but the successes of all the band members.
Jimmy Page is undoubtedly the most influential guitarist and song-writer in rock history. He can be credited with creative innovations in sound recording and experimenting with microphones and amplification. He created "reverse echo" which is evident in "whole lotta love".
John Paul Jones is an innovative producer and one of the best bassist in history. His development of classic bass lines has never been duplicated by any other bassist. He put the keyboard into Led Zepp like no other keyboardist in history, his sound is unique to him. Jones is also one of the most sought after producers and has collaborated with numerous other artists.
Robert Plant is rock history, PERIOD. He is one of the most recognized vocalists in music history. He is one of the best lyricists to ever walk, writing "Stairway to heaven" spontaneously, which went on to be the most recognized song lyrics in history (and the song was never released as a single, IMAGINE THAT). His solo career is extremely successful and his voice is recognized as one of the best tenors in music.
John Bonham is revered as one of the best drummers in history, not just by fans, but by fellow musicians, too. He was noted for his heavy, fast right foot and his use of bare hands to achieve unique sounds. Bonham is credited with the first use of drum synthesizers. "Moby Dick" is his legendary drum solo, often played for as long as an hour in concert. RIP Bonzo!
The only other band that can measure up to Led Zeppelin, in terms of influence and success, would be the Beatles and next on the list would be Pink Floyd.