Here is my review/intel for GameFAQs:
Disclaimer: I was active here a few years ago. Some things have changed. Biggest being GameSpot merger.
I believe most, if not all forums and posts are mirrored on both sites. GameSpot is more content rich, so if you like to see people's avatars that's the place to go.
In general GameFAQs is very minimal. Which in some ways is good, especially if you're a new game host. There is no font color and only basic things like bold, italic, ect. Uses < > instead of [ ]. They did add image posting, which was after my time there.
Pretty much any active forum can and does have forum games. There is a forum for every published game virtually, and new and classic game boards stay active. For example, I hosted a lot of RPGs on
Super Smash Bros Wii U Board, months(years?) before the game came out.
The moderation really wants you to stay on topic, so games in these places need to be especially relevant. For example a Smash Bros Mafia was permitted, but a Smash Bros kingdom game was removed.
There are "safe havens", secret boards and private boards among them.
The most vanilla option is
Roleplaying and Fanfiction, though activity is minimal, but viable. I have never done anything here.
EVERYBODY PANIC is a place where everyone *Panics* and avoids THE PIT where IT lives. There are a lot of random improv battle threads, design a floor of a tower games, occasionally fend EP from IT threads, and they were open to a forum game or two I tried there. Love it.
Then the meat and potatoes(and unfortunately, private) is
Games-N'-Things. Anything goes. Very active. Great people.
UPDATE: Found out you can go to the GnT link when logged in to send invite request!