Where's Spassky? He could beat the best players during his peak (60s). The players include Keres, Korchnoi, Geller, Tal, Fischer, Petrosian.
Spassky was a great player and must be very close to top ten, but he did after all not impress all that much (for a greatest ever top ten player, that is) outside those few years at the end of the 1960s. His two title matches against Petrosian showed that the two weren't separated by much, and both had indifferent tournament results. Comparing the position Carlsen has had in the world over the last years, with very dominating tournament results, huge lead on the rating list, repeatedly voted best player in the world, and winning his title match very clearly, I already rank Carlsen ahead of Spassky with regards to achievements.
Lasker when he was really old was even capable of defeating Euwe and drawing Botvinnik, that was incredible!