This is an easy one as it tick all the boxes for me. Influential album? Tick. Innovative sound? Tick. Just plain amazing music? Tick. Bluesy Rock with a great rhythm section and amazing vocals by Robert Plant. Always functional and the album sounds fresh, all instruments can be heard individually, it's not a "soup of sound". My only minor issue, as with some other older stereo albums (Beatles very guilty of this) the sound for individual instruments sometimes sits completely on one side or moves wildly from left to right and back - a bit nauseous esp. with headphones. Still, if this isn't a 5* I don't know what is.