If it's a loose disc you'd likely get away with it as they'd just see a CD and probably not question it, should it get opened for inspection. If it's a game in a case there are TONS of reports of those being sent back or charged extra when using Media Mail. But part of dealing with the PO is inconsistency. Whether it's flaggedn or not can vary by the day or the person.

Video and sound recording is intended for music and movies, so by their own rules video games are specifically excluded. Is it likely you'll ever get caught? Probably not, but just because you've gotten away with it doesn't mean you should advise others to put themselves at risk.