Hmm...I'm in two minds about Rush
They seem to have a habit of their albums either being really awesome (e.g., Moving Pictures, 2112) or embarrassingly bad (Caress of Steel). But then "best prog band" is a difficult one because so many of them release another experiment that falls flat on its face and sullies an otherwise excellent back catalogue. (If you can recommend any other good ones I would be interested to check them out)

I'm inclined to say Hawkwind, simply because their first two albums are so unlike anything else you've ever heard. Warrior on the Edge of Time is also a truly excellent album. There is stiff competition with Camel's first three albums, and Quintessence's early work. Though if we are to base it on the strength of their good albums (as opposed to say, a ratio of good:bad), then Rush have a reasonably strong claim.
(LongJohnBaldry, Sat 11 Dec 2010, 10:12, Reply)