I'm sure they'll have been said already but I would go for several Floyd albums, namely Dark Side of the Moon, Wish You Were Here and Animals.
I think it's a 'sum of the parts' case; individually some of the songs might not be particularly brilliant but when you put them together in album form I find myself just drifting along, musical perfection imo.
I can't think of many albums by other bands that have that effect on me.