That depends on the definition of 'best'. But my own list is: 1.Carlsen, 2.Kasparov, 3.Fischer.
But I also like Larsens reply: 1.Philidor, because he was much more ahead of his contemporaries than any other chessplayer has been. And this is a more fair definition of 'best', as chess constantly evolves, and any chess player stands on the shoulders of earlier players.
The top 50 list made by chess24 is quite convincing.
Who do you think is the best chess player of all time ?