If you mean active players by country, polish are very strong, but maybe not the best since there is a drop off at some point.
If less active players could be considered, then it would probably be Americans - since that is the biggest pool of players that also has some top players in it.
Regardless of affiliation, the best all around players in my opinion would be the fastest skilled players (Lone, Swift, Viruz, Player to name a few) since they can play all maps on all sets.
There’s my $.02 of shitty input