20 for the Swiss, 17 for the Spaniard and 13 for the Serb.
Cilic, Marin
[6]
Federer, Roger
[2]
Nadal, Rafael
[1]
Thiem, Dominic
[7]
Anderson, Kevin
[8]
Djokovic, Novak
[12]
Australian Open
French Open
Wimbledon
US Open
Not much age difference between Rafa and Novak really - depends if they can stay fit like Roger has. Anything is possible with these guys though.
However, I agree that one should either talk about the big three, or alternatively the big 5. If Murray counts woth three Slams, I think Stan should also be given credit.
There is one Master 1000 that he needs to win, then he is the only player who has won every M1000 at least once, but I cannot remember which one it is.
It appears to have first been coined in the US press and is necessary when referring to the [hold your tea barrel] Big 4 having dominated World #1 for so long.
I think i'd be an idiot to suggest Murray is at the same level as the Big 3 but in his own right deserves to be referenced.