A few years ago I heard somebody (and no, I don't remember who) talking about how it is getting your first album out. He said you spend years getting every song just right and perfecting your sound while you try to get signed with somebody that will put out your music. Then you suddenly get a big hit and your producer calls you up and says he wants another album next month. It explains why number 2 is frequently a dud.
I saw Led Zeppelin in 1969, great show in a small venue. I think they hit their peak a few years later with ZOSO. Best concert I ever went too was Crosby, Stills, Nash and Young a year later. I think their first two albums (although Neil didn't join them until after the first one) were their best. Drugs and alchohol were not kind to Steven Stills and David Crosby, although I hear both are sober now. I've like all of the iterations of Pink Floyd. I liked early Rod Stewart and completely stopped listening to him about 1974. And then there are bands like AC/DC and the Foo Fighters who have recorded what amount to about four hundred versions of one good song.
Edited to add, I saw The Doors in 1967, I loved them at the time, now it seems like all their music sounds the same.