Paul Morphy, let me add a reason to this, today there are still players alive who can say they have played against, Fischer, Kasparov ect. I don't know of any player today alive or anyone who can talk about playing against Paul or someone who played against Paul. His games seems to be one of the few things we have from him, my favorite player is Tal, I would like to play many GMs, but at least I can find someone who played against Tal.
If you could go thru time and play any player (past or present) who & why ?