I’ve always thought Johnny U the GOAT because he transformed pro football with Raymond Berry. He and Weeb Eubanks opened the door for a designed passing game. He basically created the 2 minute drill and the use of the sideline outs. Could he have competed in today’s game? It’s pure speculation but assuming he received the benefit of today’s training methods I think so. If transported from 1959 to today of course not. In some ways there can be 3 GOATs. Johnny U as the prototype, Elway , Steve Young, Rogers Rogers eventually Mahomes as pure athlete and or passers. Finally Brady, Montana and Bart Star as championship holders. Brady is the first to climb on Johnny U’s pedestal in my view.
Your memory's obviously better than mine. I remember Unitas as not being very mobile. My recollection is he probably couldn't break 5 seconds in the 40 if they ran the 40 in those days.
Another point worthy of discussion. Personally, I would rank Brady #1, 2 & 3 would be a toss up between Elway & Montana.