The number of posts is really an illusion. Do you know what people actually talk about in these communities? Allow me to break it down for you:
Destiny-GAF: People posting "I've got two spots left in the party, join up!" nine times out of ten.
Dota-GAF: People desperately trying to snatch their souls away from the game, but failing.
League of Legends-GAF: These guys also talk about Dota.
Halo-GAF: A group of gamers who talk about the upcoming games in the franchise and are completely unaware of how much shit the other GAF communities talk about them.
Steam-GAF: People asking about how to get 5K resolution on their four monitors for Sakura Spirit.
Smash-GAF: Reasonable and measured discussion based on logical theories and evidence.
Giant Bomb-GAF: These users have evolved beyond video games and now discuss about people discussing about video games sometimes.
TF2-GAF: Small in size, biggest in quality minus Clivefrog