I'd lean towards that late sixties cluster, too. (though Led Zeppelin 2, seminal and great as it was, didn't get as many spins on my turntable as LZ 4, two years later)
Again, a piece of my chromosome got broken off with the ranking things gene, so all I've got are 60s-70s LPs floating in memory - Abbey R, Let it Bleed, Tommy, LZ 4, Taser and the Firecat, Goodbye YBR, Sticky Fingers, Night Moves, Van Halen debut album, Moondance, Machine Head, Aqualung, Dark Side of the Moon, Boston debut, and a hundred others, all with moments and people and places attached like remoras of memory and making any objective comparison fruitless. I could say some of those albums were perfect - Deep Purple's blend of blues and nascent metal in Machine Head, Pink Floyd's DSotM, Who's Next, Bat Out of Hell, and others that just didn't waste a note.