Sally Simpson: That post got me thinking...Who has played the most World Champions, not beaten, but played. (World Champions as in tracing the line from Kasparov in 1993 to the present and leaving out the years when the title was in two hands.)It must be, it must be between Reshevsky and Korchnoi.
Reshevsky (10):
Lasker, Capablanca, Alekhine, Botvinnik, Smyslov, Tal, Petrosian, Spassky, Fischer and Karpov.
Korchnoi (11):
Botvinnik, Smyslov, Tal, Petrosian, Spassky, Fischer, Karpov, Kasparov, Kramnik, Anand and Carlsen.
I think that is right.
If Korchnoi had beaten both Anand (P5 D5) and Kramnik (P.5 D5) he would have the most wins v World Champions and if Caruana one day becomes World Champion (it's possible) we can add him to Korchnoi's list as having played against and beaten.