10. King Crimson
If it weren't for King Crimson, the entire prog landscape might not exist. Under the watchful eye of guitarist Robert Fripp, the band toyed with everything from time signatures to different recording techniques in order to make their music sound like nothing else in the rock sphere. Though the band would have other epic tracks, it still doesn't get any better than In the Court of the Crimson King.
From the way "21st Century Schizoid Man" marches in with its use of distortion to the moody energy of "Epitaph," the whole album feels like you're listening to the sonic equivalent of the rapture. However, things began to unravel once the band got to their next record. In the Wake of Poseidon was still a great helping of prog, but with members Greg Lake and Michael Giles already out the door, the band had lost some of that initial magic. Though later albums like Red and Larks' Tongues in Aspic are still phenomenal by prog standards, they don't possess the amount of punch that the band's first record had.
Saying that King Crimson never got better than their debut isn't really the diss it's supposed to be. In the Court of the Crimson King couldn't be topped, but that's because most other human musicians probably couldn't match it.