I tried to figure out which two players of the modern era have played against each other the most times. I looked only at the last 30 years or so to keep the search simpler, but also because when there were fewer teams in the league, they played much more often. For example, in the calendar year 1960, Bill Russell and Wilt Chamberlain played 18 games against each other!
I searched around and couldn’t find anywhere this information existed. So I did some research. Assuming that to have the all-time record you’d need a lot of playoff games, I found the list of most playoff games played and started comparing players using Basketball Reference’s Head2Head tool.
The highest number of head to head games I could find is Derek Fisher and Tim Duncan, who have played each other in the regular season 49 times, and in the playoffs 47 times!
Though the number of wins is close (50-46 advantage for Fisher), unsurprisingly the stat contests easily favor Duncan. He averaged nearly 19 points and 12 rebounds a game, while Fisher averaged about 12 points, 2 assists and less than 2 rebounds per game.
Fisher and Duncan faced each other in the playoffs 4 years in a row, from 2001 to 2004.