I don't really intend to collaborate on one project, 22 people already showed interest, that's 15 people too many for something like that. Everyone will make their own Tetris / Mario!
Indeed. And think of the sheer number of games we'll get out of it :-D
A GitHub isn't a bad idea though. We could make a GOG Community Game Development GitHub, then we could each have a folder to ourselves, with subfolders for the various projects we will be undertaking. It could also function as a central repository for showing off our work. And of course, if some people do want to collaborate on something eventually, it would make it a lot easier.