Greating everyone, I would like to contribute something but since English isn't my native so I will try to explain it the best I can.   
About the sub-forum for each game. 
I thinks the idea is ok and workable.   
But as I have seen some previous posts mention about problems of "the number of games that will constanly grow" and "not interesting/low content to dissuss" 
yet the idaa of having all the game being sub-forumed is still essential otherwhile it might turn into free-for-all and mass up the forum   
so I suggest that in the front page we show only the most recent activity of 5 or more game's subforums in this way if some unusaul game does have a new activity everyone can see and respond to them. 
And of cource with one sticky topic to act as a game's sub-forum directory.   
So it might be like this   
-Games Directory-   
-subforum1 (most recent activity) by whom, time, topic, etc 
-subforum2 (second most recent) 
-subforum3  
-subforum4  
-subforum5    
I dont actually knew if it possible or not to have the entire sub-forum move up and down like a topic, if some activity turn up. Since I have no exprience with organizing a webforum, Still I like to express the idea in case it may be of help to the future forum.