We should all agree that GOAT is a very relative concept because the changes in conditions, technology, training, the tours,politics and, of course, the competitive level of the top 10 or 15 players who are the ones challenging for the big championships.
The concept of major itself has changed.Till the 1950´s, Davis Cup wins counted as much as a traditional slam or, in the case of pros, a pro major win.In the 70 and 80, WCT and Masters were majors de facto as opposed to the Australian, which was still an official slam title but felt short of those two events.
Indoors on fast carpet and formerly wood were big while there were almost no important hard courts tournaments, just the polar opposite of modern times
I think we should decide who is the goat in the context of his or her era, how much and long dominates, how diversified his or her major accounts, what level of competition he or she dominated and so forth.and of course, how well she or he played the game or how close was to " perfection" if such a thing exists.
That said, I´d propose to , first determine, relatively homogeneous eras and then, pick up the top 10 players of each.At the end, however, we should pick 15 or 20 because that´d give us a much wider idea of the real level of competition atop.
To me, it´d go as follows ( and I have already posted that before):
1900-1929: Tilden,Wilding,Cochet,Lacoste,Doherty,Brookes and Borotra with Williams,Decugis and Richards as minor champions
1930-1949: Budge,Perry,Kramer,Vines,Crawford,Parker,Riggs,Von Cramm,Nusslein,Kovacs
1950-1959: Gonzales,Rosewall,Hoad,Sedgman,Trabert,Kramer,Segura,Patty,Drobny,Seixas
1960-1969:
Laver,Rosewall,Hoad,Gonzales,Emmo,Santana,Gimeno,Fraser,Cooper,Anderson with Olmedo,Stolle and Pietrangeli who could spot also the tenth place
1970-1979
Borg,Connors,Newcombe,Nastase,Vilas,Rosewall,Kodes,Ashe,Smith and Orantes.Mc Enroe,Panatta and Gerulaitis could also challenge Orantes for the number 10 position ( although Orantes has the best overall record)
1980-1989
Lendl,Mc Enroe,Wilander,Becker,Borg,Edberg,Connors,Noah,Cash and Johan Kriek
1990-1999
Sampras, Agassi,Rafter,Courier,Bruguera,Ivanisevic,Stich,Muster,Chang,Krajicek and Kafelnikov or Moya
2000-2013
Nadal,Federer,Djokovic,Kuerten,Murray,Hewitt,Safin,Roddick,Ferrero,Wavrinka,