What is a god? It is a thing we put our faith in. It is a thing that inspires us to move forward, to be better than ourselves, to become part of something larger than ourselves. We all have gods. They may not be Gods, but they are gods nonetheless.
(this may not translate well for non-native English speakers, and for that, I apologize).
In American Gods, Neil Gaiman describes how just about anything can become a god. That the modern gods of American culture are Television and The Allmighty Dollar (that last one might have been White Wolf Game Studios, as they had a similar device in Werewolf: The Apocalypse). That if enough people believe in it, it becomes a god, even if it was never one to begin with.
Who is our first god? Our family. Our mothers, fathers, and siblings. So it makes sense that Akira's first god is his brother -- the person who was his equal in status, but his superior in every way. Our parents are authorities, but our brothers and sisters, even the ones with significant age gaps, are our peers. And so he came to view his brother as his first god, the person to look up to, to aspire to become. And how did he see his brother? Well, his brother fucked everything that moved.
Note, however, that his brother's wife isn't a god. She is, quite literally, his World. That which he came to live for, that which he came to desire beyond anything else. I don't think pre-loop Akira ever actually loved Niki. I think he was with Niki because Sekai got off on watching him corrupt her, and when Sekai died, he no longer had a reason to spend time with her.
If you're a young, awkward kid growing up in any era after the proliferation of American On-Line, your second god was the Internet. Social media has ruined the internet in many ways. The game is set in 2020, so Akira was born in 1989. A young, awkward Akira would be discovering the internet in late 90s. When it was still the glorious refuge from the bullies outside. Thus, it makes sense that the God of Wires is his second god. And the Akira of the time loop never spends time on the internet, so it makes sense that the God of Wires is dying -- gods need attention from the faithful to survive, after all.
This makes me wonder why Pareidolia is the third god. The first two make sense. But how would the tendency to see a defined image in a random pattern become a god?
Until I saw this while I was googling Paeidolia:
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