Sorry. Can't agree.
Pink Floyd, as Andalucia said, in their Gates of Dawn days, were good.
After that however, they just fell to Waters' pretension. He wasn't even a good writer! If you look at any Floyd material it's excessively boring, while trying desperately to be prog. C, G, E, Em, C, Am. What the fuck?
Now I'm not saying simple can't be good. Look at Nirvana say, or Jane's Addiction. But for prog it doesn't cut it.
King Crimson were essentially a bunch of extremely good musicians, with interest and history in Jazz. This allowed them far more freedom in what they were doing.
I fail to actually think of anything Floyd did that was interesting, post Barret. I have tried to like them, and I have tried to see genius in them.
T-Rex, I'll concede, they had their moments. They were never a classic, but they had their moments.
The Mars Volta, I see as prog, in some ways, because they are doing the same kind of thing as Crimson. They are shucking all idea of convention. They do what they want, when they want. They'll throw a song round halfway through, and then do what they want with it. That's all there is to make them prog, but there's nothing much more to define prog. It's just people doing what they want with music really. Any band who break down into 5 minutes of wailing sound and echoey feedback during a jazz riff laden song that hasn't followed the conventions of verse/chorus/verse, what else are you going to call them!?
But man, it just pissed me off that Floyd are considered some sort of musical visionaries when they did fuck all.
Anyway, don't mind me, I'm allowed to be excessively opinionated in here, 'cause I say so!