Lots of bands really, the obvious ones are Yes, Genesis, Mike Oldfield & King Crimson.
If I think about your second question I doubt I would have gotten interested in King Crimson's reverse catalog until they got to Discipline, I'd probably go backwards (or forwards) and explore after that. The classic artist for me would be Mike Oldfield as I doubt I would have picked up any of his catalog if I had to wait something like 20 albums before he released Incantations.
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