Possibly not big sellers but "Dark Side Of the Moon" was in the top 100 album sales for a ridiculous amount of time, something like 400 weeks. I'm checking now, don't want to misstate it. From Wikipedia: The Dark Side of the Moon has spent 741 weeks on the USA-based Billboard 200 album chart, the longest duration in history.[7] It is also the fifth highest selling album globally of all time, selling more than forty million units.[8]
I also enjoy the Celtic rock bands from that era. Steeleye, Fairport Convention, but most of all the Strawbs, who were after all, the band that begat Rick Wakeman.