Listing the greatest guitarists or greatest singers or such seems just too broad to get the best results. For something more narrowly focused, let's look at individual songs with the greatest rhythm guitar parts.
Looking to tease out the best rhythm guitar performances leads to some consideration of what even constitutes "rhythm guitar." Some of the stuff is not strictly chords, but riffs or some of both. You'll see.
Some of the best guitar work, especially rhythm guitar parts, don't obviously dominate the song. A good example of this is "Sign O the Times." The guitar part is so sparse and understated, but so precise that the whole song doesn't quite make sense without it.
Another problem: I have trouble picking out a good rhythm guitar performance to represent some of the biggest guitar hotshots. What Jimi Hendrix song would you pick out to represent him playing "rhythm guitar"? Likewise for Jimmy Page.
Ah, well, we do the best we can. To that end, then, here are the official, 100% objective Al-picked greatest rhythm guitar performances of the rock era:
1) "Love and Happiness" John Mellencamp - Strictly on the basis of the rhythm guitar, no song in the rock tradition lays out a more perfectly dramatic presence than this lesser known Mellencamp classic.
2) "Maybellene" Chuck Berry - If you had to pick out one musician as the main architect of rock and roll, it would have to be Uncle Chuck. In this first single, he defined the basic jumped up blues guitar rhythms that were the original DOS programming of generations of musicians.
3) "Papa's Got a Brand New Bag" - James Brown This record pretty much invented funk as we know it today, including a new conception of guitar rhythms.
4) "Black Betty" Ram Jam - This studio concoction managed to take a Leadbelly song, and turn it into ultra heavy metal and sheer joyous bubblegum all at the same time. The jumping chord figures turn this into a lead rhythm guitar. This is definitely one of the more awesome rock records ever.
5) "Mystery Train" Elvis Presley - This early Sun record defined the jumpin' country side of the early rock equation.
6) "You Really Got Me" The Kinks - Along with the even slightly better "All Day and All of the Night," these two chords were not just career makers for the band, but one of the main beginning points of power pop and even heavy metal.