Why do the Egis appearance look awful and unimpressive

[Exodus-E]

I mean, Ixion instead of Ramuh? What the hell FFX. Clearly not a real Lightning Summon, the developers should have fixed that for the HD rerelease.

The (most likely) reason for that may be same as to why FFVIII didn't have him as well (instead, we had Quetzacoatl): because the summons on those games could be "trained" and "taught" new stuff, something that would've been redundant/useless for someone as old and wise as Ramuh.
Thus, why they had to replace him with something else.

I'm more concerned as to why we didn't get Leviathan on FFX though, given how big the whole theme of water/sea was in that game (not to mention that it didn't even have any Water-based summon to complete the four-elemental ones)...now THAT's something I would have love to see on the HD re-release.