Who Is The Greatest Chess Player That Has Ever Lived ???

     The famous Mechanical Turk that Napoleon played in 1809 was not a chess engine. It was a large elaborate machine which had a statue of a Turk move the pieces. The secret of the machine was that there was a man inside. The owner of the machine found a professional chess player willing to take a percentage of the substantial sums the "amazing thinking machine" made in exchange for spending hours at a time uncomfortably crammed inside the device, and remaining anonymous.

     Napoleon was interested to see if it really was a mechanical device so he broke the rules by moving first (the Turk always had white) to see if it could respond. It did. Then he made an illegal move to see if the machine would know what he did. The Turk put the piece back and waited for Napoleon to move. This time Napoleon tried to see if the Turk would notice that he made two legal moves simultaneously. The Turk just knocked all the pieces off the board.

     Satisfied that this wasn't actually an unthinking machine but rather just a trick, Napoleon played a game vs the Turk and resigned after 18 moves, hardly surprising as the hidden operator was a strong enough player to have given Philidor a good battle while the Emperor was a notoriously wild player.

morphy.

I enjoy history, and chess history especially. But the question wasn't who is the greatest person who ever lived to play chess. The question was "who is the greatest chess player who has ever lived?". That rules out people in the future, engines, and most sock puppets. 

This is a great subjective question. The best player who ever lived is, objectively, Magnus Carlsen. The greatest chess player is for me one of a short list:

Philidor (the player who was clearly the best player in the world for the longest period, and influenced pretty much every great player since)
Paul Morphy (an inspirational player who taught us many of the modern principles and especially how to play open positions. He also inspired many with his blend of Romantic ideas and scientific breakthroughs)

Wilhelm Steinitz (the first World Champion and perhaps the first true professional. He sought to systemize the rules of positional chess)

Emmanuel Lasker He is generally listed as one of the five greatest because he held the official title the longest (27 years), dominated chess for many years after he lost the title, and often outperformed Capablanca and Alekhine despite his advanced age. His writings on chess also propel him ahead of others

Jose Capablanca Although he only held the title for a short period, his seemingly perfect positional play and his writings made it seem like he reached the pinnacle of chess understanding. His play is a great model for young players learning how to play "correctly"

Mikhail Botvinnik often overlooked, but the Patriarch of Soviet Chess. He embodied the dynamic school of chess and his 1938 victory over Capa has been rated as one of the greatest and most important games ever played. It symbolized a change from pure classical chess to dynamic chess. He also pioneered computer chess and led a school that included many Soviet and post-Soviet players, most notably Karpov and Kasparov. 

Bobby Fischer He was clearly the best player ever to play the game until at least 1975, and more importantly, inspired generations. He was the epitome of objectivity over the board. He always strove for a win, playing in beautiful classical style as White but in a vigorous dynamic style as Black. He was capable of brilliance, but abhorred speculative sacrifices. He was a founding member of Pawnsnatchers Anonymous, and his single most famous opening was the Poisoned Pawn variation of the Najdorf. 

Perhaps his greatest contribution to chess wasn't his games (he played less than 1000 official games), but his inspiration and his drive for professionalism in chess. He made chess an international sport that everyone talked about. 

I will add more about the three most recent candidates for greatest ever later:

Anatoly Karpov

Garry Kasparov

Magnus Carlsen

Spoliers: While I consider all of the above to be legitimate candidates for greatest ever, I rate Magnus Carlsen and Garry Kasparov as the greatest ever, with Magnus edging out Kasparov. 

Confucious says roads were made for destinations not journeys

""We are like dwarfs sitting on the shoulders of giants. We see more, and things that are more distant, than they did, not because our sight is superior or because we are taller than they, but because they raise us up, and by their great stature add to ours." - John Salisbury

That giant is Greco.

Thanks a lot for the posts and the info.