I havent really paid too much attention to ranking the all time top 5 but if your question is who has been better than C.Ronaldo.
Zidane Crujff Platini Maradona Pele and Brazilian Ronaldo before his serious injury (actually this guy would be the real goat should he avoided that nasty injury).
On top of my head these names quickly emerged but I dont think you can call a player the best of all time without taking reference to his position
C.Ronaldo in his position is indeed top 5.
Its easier when talking about GK though - Buffon and Yashin are the only real contenders here and while I havent seen much of Yashin I have seen enough of Buffon and he is to me the GOAT GK.
Zidane, Cruyff, Platini, Maradona, Pele are one of the most synonymous names in football. You just can't really put those above CR. Nothing really suggest they're better or more great than CR is. Of course, it's an opinion but there needs to be something else than opinion included or otherwise you could name anybody. Titles, Stats, Longevity, Influence, Era's etc. needs to be taken into the account.
With R9 it will always be if, could, should and would = did not happen. There's actually quite many players like that in different sports, but there's always reasons why it never happened. That speculation is unecessary, because it simply never happened.
Yashin vs Buffon, so you based your experience on for what you have seen, so it's not really a real way to put it. Or is this Youtube as an experience about the player? Can you really build a proper image about the player from the google etc.? I would never even go so far, that i would even try to judge the players i'v never seen, neither even bringing to GOAT discussion because it will always be more like someone else's opinion than yours. It will always be based on stats, very limited footage and words from the co-players.