It’s an interesting question and it depends on how you make the comparison. I said Carlsen here because I think if the chess greats were to play against each other in their prime, Carlsen would have the advantage simply because of today’s expanded knowledge of the game. In other words, he’s analyzed positions (often with the help of computers) that were less explored in previous generations.

Kasparov partially advances this idea of progress in chess in a fascinating interview. He also brings up a different metric: who was dominant the longest, a judgement in which Kasparov is the clear winner! (He also emphasizes how he was a rare case of a chess champion who was able, at the end of his career, to “beat the next generation.”) Kasparov also brings up a third standard: who was the farthest ahead of their contemporaries? In this case, he suggests one would probably choose Bobby Fischer, although his massive edge was short-lived.