Adult game is a polite way to say the same thing.
Porn game, while accurate, comes off as a bit too direct.
Doom is definitely a "mature game", but you wouldn't call it an "adult game". The phrase "adult game" usually implies more sexual content than violent content.
Viewing post in Futaken Valley ver 0.031.55 comments
Yes, I know well what it means, but the word "hentai" and "eroge" is generally what legitimate sites (like Steam, GOG.com, etc) usually used, unlike the word "porn."
That's why I advise to use the word "adult," instead. Because what word is used sometimes matters, even if it means the same. You don't call a young girl you just met "woman" or "female," right (hehe, like what Vegeta did)? You call them "miss" or "young lady," instead.
But then again, it's up to you if you want to accept my advice or not. It's just simply me suggesting you, I mean no harm, and you don't have to reply this or continue the discussion.
Edit: Oh, I notice that you changed it. I appreciate it.