Hello all, saw this thread, and had a couple of games to add to the discussion.
First, there's an unreleased Game Boy Color game called Infinity. It's a Zelda-type action RPG that was in development around the time of the release of the Game Boy Advance. According to the website, it was ~90% complete before development stopped, so any work porting it to the DC may be a little involved putting all the existing pieces together. A prototype ROM, along with the source, is available here:
https://infinity-gbc.org/
Another game that looks like fun is a retro-style PC game called Strange Flesh. Fair warning, it's adult-themed. so NSFW! It plays like Streets of Rage, and is currently available for free on its website. A few reviews I've seen praise its music, but say overall the game is a bit short. As it was made more recently, I don't know how feasible a DC port would be. All info about the game (remember, NSFW!) is available here:
https://greatestbear.com/strangeflesh/
You can access the source without the adult-themed material here:
https://github.com/UrsaMaximus/Strange-Flesh/