One cannot rank Sampras ahead of Nadal when Sampras never won the French Open while Nadal has won all majors multiple times.  Nadal is virtually unbeatable on clay but is hardly a clay court specialist.  Winning both the US and Australian Open multiple times confirms his versatility.  Sampras is more a specialist than Nadal.

Laver is the best player of all time.  Two Grand Slams, one in the Open era, versatility to his game...no question he is the best all time.  Fed is second.