Mosconi is probably the GOAT and, with fifteen world championships, he may always be, but in the 9ball era, most agree that it is Efren Reyes. I'm sure Efren already understands that Filler may well replace him as the 9ball era GOAT.
Filler mass produces major titles (big and super-elite internationally diverse field), at a rate that nobody has since Mosconi. At 27, Josh has won all of the a) World 9-ball, b) World 8-ball, c) World Games 9ball, d) China Open 9ball, e) US Open 9ball, f) UK Open 9ball, g) European Open 9ball, and h) Qatar Open 9ball. He wins titles in every discipline, wins major titles all over the world and, like Efren before him, he wins when the prize money is highest.
In my 49 years of regularly attending pro events, I have never seen anyone play the game as well as Filler. Like every superstar that came before him, he is beatable, but it typically takes a very special performance to beat him.
In my GOAT discussion, there are only Mosconi, Reyes and Filler.
billy incardona said something along those lines in commentary (hotseat match), that he was the best player he's seen. it was nice to hear billy doing comms again. he's still an astute observer, and knows so much about one pocket