1) Bohemian Rhapsody - To me this one is a no-brainer because the operatic arrangement for a rock song is classic Freddie Mercury, who was a true artist with the greatest vocal range of any.
2) Space Oddity - David Bowie was certainly an all around artist in everything he did. This song is so creative with its studio affects.
3) Uncle Albert - Paul McCartney hit it out of the park with the crazy mix of music from segment to segment in the song and of course the awesome and funny, additions that they added in the studio such as underwater sound.
4) Band on the Run - My bestest Paul McCartney again (and The Wings). The way the song transitions from a mellow beginning to hard rock music with tremendous guitar playing, makes a person want to get out up out of their seat and jam.
5) Stairway to Heaven - Led Zepplin absolutely blew the world away with this song. It was one of the most black marketed sound tracks for young people in Communist countries. President Reagan definitely led the charge for breaking down barriers with Communist countries, but the fact is, the underground music world changed hearts and minds and places like Russia couldn't stop it. Remember the Beatles playing there? The kids at the concert looked like American kids all jumping around and screaming.
So many more I could've listed, but there's no doubt I've probably played the above songs thousands of times in my lifetime. These songs are pure genius.