In our opinion, selecting one game per each genre is a powerful concept because:
provides enough variety in the games list, while keeping the set relatively small
selects the projects who have the potential to become the best in their genre, inspiring other developers to join their effort and make the game better and better
ensures there is no competition between the selected games, so those can more easily join their forces in advertizing and promoting all participants of the Alliance
makes every project feel special and unique inside the Alliance, making the discussion between the developers a real learning experience
provides to players the perfect set of games, so those can be expanded endlessly with new content
helps new developers to join forces around a single game per genre to have one finished product instead of 10 never completed!