Who was the greatest chess player of all time?

Who?

Was it Alekhine? Capablanca? Robert Fischer, Garry Kasparov, Magnus Carlsen?

I think Carlsen is the best up to date.

In terms of playing accuracy: Carlsen.

In terms of achievement: Kasparov (from the list) an argument could be made for Karpov.

In terms of contribution to chess: Fischer (from the list) otherwise Steinitz and maybe Botvinnik.

In terms of dominance: Capablanca/Fischer/Kasparov.

yes probly true

Although Nimzowitch never was a WC he brought chess ideas to the modern chess world long before they were accepted and used by many WCs.

Mikhail Tal for complication

Then Siegbert Tarassch also there as Aaron Nmzowtch

Richard Reti and Savielly Tartakower also contributed to hyper-modernism as well.