Someone said it before, dont know if in this discussion or elsewere, can you ever compare those players? See: Brook is a Center, Gallo a forward and for arguments sake, Mayo a guard.
Brook will always be the better posting up, rebounding and defending the paint. Gallo will always be the one with the snipers touch and the all around awareness, while Mayo will be the quickest, most agile of the 3. You wouldnt compare Nowitzki with Vince, even when they were both drafted in '98...
What really determines players in the end, is their success. Duncan will have had a better carreer than, say Malone because he won all those rings and Malone hasnt. What makes a player the great one he might become depends on so many variables, its not even funny!
So, be happy we got Gallo, wait a few years and see him starting alongside Brook Lopez at the All Star Game 2014! In the end, around 2020, we will say Gallo won a few rings for NY while Brook always got short of getting out of the first round with his Brooklyn Nets. Then you can say Gallo was the best of his class, everything else is Fubar!