I'll roll with The Wall. Maybe the best classic rock album of all time. Floyd's 4-album run from DSOTM, WYWH, Animals and The Wall is quite possibly the best run in music history. The only thing that comes close IMO is the Stones run of Beggars Banquet, Let It Bleed, Sticky Fingers and Exile in Main St. A case can also be made for the Beatles run of Rubber Soul, Revolver, Sgt Pepper's and The Beatles except that Magical Mystery Tour reared its sometimes ugly head in the middle.