Everyone is overhyping Giorno while ignoring the crazy amount of abilities Gilgamesh now has access to.
“Avenger is able to escape from even 'abstract prisons such as time and space.' Through performing super high-speed thinking, he is able to forcibly reflect that on his body and 'subjectively realize a super high-speed action that makes something that seems like a 'time halt' is being employed.” (Edmond Dantes)
“The ten Rings that Solomon attained Omnipotence, given by God. The mark of the king, the progenitor of magecraft. In the case of all ten rings present, any and all kinds of magecraft performed by mankind is invalidated and put under his subordination.” (Solomon)
“It is a kind of teaching to achieve final Moksha, where energies rivaling the law of man’s creation are made to converge on a single person and liberate him from suffering. As the length of human history increases, with its expanse becoming wider, the greater the damage of the attack, and the humanity of Earth has no way of withstanding the attack theoretically.” (Buddha)
“By summoning an array of magic circles, she then makes a powerful strike that unleashes a pillar of light through the array of magic circles similar to Teardrop Photon Ray to destroy the target. It is powerful enough to even overcome the Velber Ark's multidimensional defenses set up by Archimedes.” (Saber Venus)
Goku definitely isn't taking this. He won't be able to defeat Giorno due to GER, and he can't kill Gilgamesh since Avalon will make him completely invincible.
Odds are either Giorno wins or Gilgamesh does. I'd say Gil does, as he can use the Noble Phantasm 'Gae Bolg' to bypass GER and defeat him, meanwhile Giorno has few to no ways of defeating Gilgamesh.
Avalon is pretty overpowered.