@horrormakerI would put Fischer, Karpov and Kasparov at all about approximately equal in strength, given that there was about one clear decade between these three ...something which does matter quite a bit. Those chess heroes from many decades before like Capablanca, Lasker, Morphy etc just too hard to evaluate.
For sure all of today's top 50 superGM's are far more knowledgeable overall than any of the above in Chess ...but Fischer, Karpov and Kasparov were all so very special, albeit in some many very differing ways.
Pity that Karpov-Fischer never happened, even for one single game - though they both crushed Spassky (who was very strong and very tactical and very attacking, if quite a bit lazy qua workrate). Both used the same idea or approach of utilizing new and surprising openings to avoid Spassky's known openings. Same idea as in all WC matches. Try lines that the opponent is maybe not so familiar with.
Same idea in Caruana-Carlsen at this moment too. Make the fight revolve more around not so much previously explored lines. In games 1 (and just now in game 3) the fight is still centering around the Nezhmetdinov-Rossolimo Sicilian way of taking on c6 with the white bishop.
Rashid a Soviet IM (never a GM, though the GM title was only awarded by committee in the '50's when Rashid was already 45 y.o.) Rashid Nezhmetdinov an utterly brilliant chess tactical genius (and an early Karpov trainer) used the Rossilimo Sicilian so many times as White, to great effect.
It's just so very nice to see Caruana-Carlsen now playing the Nezhmetdinov-Rossilimo variant of the Sicilian at the very highest level of the game. Nezh was beyond belief in attack and very often chose this simplistic attack on the basic Sicilian defence. Fischer also resurrected openings long-dead, as did Karpov and Kasparov too.
Now we are see a super battle in Caruana-Carlsen in this rarer line (new moves even possible on move 10 or so). Very fascinating this new exploration of some very old lines, at the very highest level of the game. Long may it continue!