Honestly. I think Pogi is already the BOAT. But to be the GOAT, 3 Tours, a Vuelta, and a P-R and he’s ahead of Hinault.
To be ahead of Merckx, sheesh - needs 3 Tours, Vuelta, another Giro or three, P-R at least once, plus keep racking up LBL and IL wins. Needs MSR, too. Can’t believe Merckx won it 7 times. That honestly to me shows that times have changed. Someone convince me he’d win it 7 times in this age.
But since the question was just about GTs, I’d say 3 more Tours, a Vuelta, and 2 or 3 more Giros or Vuelta and he’s #1.
Contador has 3,3,3 and no ones calling him anywhere close to the GOAT of GTs, so 4,1,0 is nowhere close either (even if he’s the BOAT…).