My dad says among these Frenchmen, they were Kings of the World:
Les Quatre Mousquetaires (The Four Musketeers)
Their names are enshrined forever: René Lacoste, Henri Cochet, Jean Borotra, Jacques Brugnon
From 1926 until 1930 a musketeer, Lacoste or Cochet, was ranked No. 1 in the world and in 1926 and 1927 all four musketeers were ranked in the top-10. They won 6 consecutive Davis Cup championships when Davis Cup was equivalent in prestige to today's Fifa World Cup.
The "Crocodile", Lacoste, won 7 singles majors (3@FC, 2 @WC, 2@USC), 2 doubles majors,
Cochet, also won 7 singles majors, (4@FC, 2@WC, 1@USC), 5 doubles majors, and the French Pro Slam as a professional.
Borotra won 4 singles majors, (1@FC. 2@WC, 1@AC), made 6 other finals, only losing to his countrymen Lacoste and Cochet, and won 9 doubles majors.
Brugnon won 10 doubles majors. His best singles result was a SF at Wimbledon and 5 other QF.
In contrast, the "New Musketeers" - Jo W. Tsonga, Gael Monfils, Ricard Gasquet, and Gilles Simon, though good players, have had trouble reaching the pinnacle, not a slam title among the bunch, but they did achieve a single Davis Cup win in 2017 though Monfils and Simon did not play in the final.
Tsonga lost his only major singles final, made 5 major SF, and 9 QF and 18 titles overall, including 2 Masters1000, and a final at the YEC. Monfils made 2 major SF, and 7QF, and won 10 500/250 titles . Gasquet has 15 250 titles. Simon has 13 250 titles and 1 500 title.