You couldn't sell that game, even if you created your own assets, because Mega Man is a trademarked character. You could make a game inspired by Mega Man, but if you use any characters or locations from Mega Man, you would be violating their trademark.

AI, celebrity likeness, and trademark is all new territory, and the courts are still sorting out how corporations are allowed to use a celebrities voices and faces without their consent. Last year, Tom Hanks sued a company that used an IA generated version of him for an ad, but I think it's still in court. How the courts rule on cases like this will probably determine how you can use AI generated voices like in your Reptilian Pope example (though in that case, I'd be more worried about a lawsuit from Futurama).

This lawsuit is a little different though; they're sidestepping the issue of likeness and claiming that AI is stealing from Carlin's works themselves, which are under copyright. It's more similar to the class action lawsuit against Chat GPT, where authors are suing because the chatbot was fed their works to create derivative works without their consent. That case also hasn't been resolved yet.

Edit: Sorry, I also realized I explained trademark and copyright very poorly. You can't make a Mega Man game because Mega Man, as a name, is trademarked. You could make a game that has nothing to do with the Mega Man franchise, but if you called it Mega Man you would violate the trademark. The contents of the game (levels, music, and characters) are under copyright. If you used the designs of any of those characters but changed the names, that would violate copyright.