The most archetypal classic Progressive Rock?

mathman0806 wrote: I say Yes and Genesis.

I didn't give reasons, but I think part of it is that in addition to having the long and 'complex' songs that showcase musicians hip, these bands had the structure of the 5 person band with guitar, bass, drums, keyboards, and vocals. That structure is carried over in the beginnings of neo prog with acts like Marillion and IQ and in prog metal in Dream Theater.