what do these greats have in common ?

of the famous players mentioned below what do they have in common in terms of study achievements style etc... anything really.

Paul Morphy

Emmanuel Lasker

Jose Raul Capablanca

Alexander Alekhine

Mikhail Botvinnik

Bobby Fishcher

Garry Kasparov

chess

Though all are "world champions," they span such a long time that the development in the understanding of the game has to be taken into account.

Morphy played the exact same game as Kasparov, but you'd hardly know it by looking at the path of development, positional understanding, defensive technique and opening selection. However, when the attack starts, all these guys look pretty much the same: deadly.

No facial hair?

Pics of a young Alekhine had a trim moustache, unlike Lasker's dry mop.