When I say superboss, I mean any boss in general that is more difficult to defeat than the Final Boss. So examples would be Kaiser Dragon in FFVI, Enuo, Omega, Shinryu, and their stronger counterparts in FFV, the weapons in FFVII, etc.
So between Zeromus EG (GBA Version), Brachioraidos (GBA Version), Geryon (DS Version), and Proto-Babil (DS Version), which superboss do you think represents FFIV the best?
Zeromus EG
Brachioraidos
Geryon
Proto-Babil
For me, it would have to be a close call between Zeromus EG, Geryon, and Proto-Babil since Brachioraidos is just a palette swap of a yellow/green dragon.
Zeromus EG has technically been around the longest between the three, since his sprite was the one that was used for Zeromus in the Easy Version of the Japanese SNES FFIV. Geryon may seem like he was a random addition to the DS Version, but seeing how he was a demon in Dante's Inferno, similar to the other four fiends (Scarmiglione, Cagnazzo, Barbarrica, and Rubicant), and the fact that he's superior to all four of them in mythology, it makes sense for him to be included. As for Proto-Babil, he also makes sense seeing how he's the prototype of the Giant of Babil. Though, facing another version of the Giant of Babil is a bit, repetitive, even though you didn't actually fight the first version head on. And to me, it doesn't really make sense that you fight him on the moon.
I guess my vote goes to Geryon since he's the only one that isn't that similar to another enemy. Though at the same time, he might not really represent FFIV all that well because of that same reason.