The K-K sequence of matches is unrivalled in competitive sport. In Portugal at the time there was much information regarding this match, but I remember following it on the weeklies chess programms with expert commentary on the chess as well as insights into all the backstage shenanigans. The introduction, playing Prokofiev's Dance of the Nights to the backdrop of snowy Red Square was unmissable and a brilliant entré to the great chess battles that followed. After the resumption in 1985, the climax came with game 16 when Kasparov paralyzed Karpov on move 16. I just had to look it up to freshen my memory. Karpov couldn't move a piece without provoking disaster to his position. Perhaps the most brilliant display of Kasparov's genius and unlikely that any grand-master has ever achieved such a dominant position in a chess championship match before or since.
The rating system in international chess (Elo, designed by Arpad Elö) is incapable of comparing playing strength between players from different time periods. It is designed to facilitate a comparing of a closed group of players. More so up until the seventies there was no rating-system in place. You also have to take into account that the rules have significantly changed over time, specifically time-limits.
If you're into chess, read on.