Yes, in a vacuum Sonichu is just a mishmash OC. But the story of Sonichu isn't just Chris being Sonichu's pokemon trainer or something. A lot of interesting stuff happens. Remember there was a LONG period between when Chris created the Sonichu character, and when Chris actually started creating Sonichu lore. After a couple of issues it stops just being Pokemon with Sonic powers.
And yeah Chris steals a lot of ideas, but ultimately that's what all creators do. You have to remix just enough, and eventually it does become something original.
Anchuent Cherokians (that resemble Mormon-style lore), people struggling with their sexual identity, a dark force that is the personification of growing up and having to take responsibility, one man's struggle against an oppressive system, etc.
It's all very childish, but it actually is pretty deep when you analyze it.