grammaticality - Which one is grammatically correct: "one of the great" or "one of the greatest"?

I have been playing a typing game for a while now. The text starts with:

Aesop was one of the great Greek writers...

Is "one of the great" grammatically correct?

Answer

Aesop was one of the great Greek writers...

and

Aesop was one of the greatest Greek writers...

Are both grammatically correct and mean the same.