I think people often overrate the "idea/concept". If I say, I'd like to make a platformer with a flying pig, well, it could turn out great or totally suck. It's not a bout the idea/concept, it's about what you make out of it. It's about how the individual levels look like, how responsive the gameplay is, if the flying pig has a funny gimmik or not, etc.
However, like the saying goes "too many cooks spoil the broth" ...because to some extend making a game is like cooking, and if everyone wants to contribute slightly different ideas, it'll tear the development it many directions instead of one ...because, let's not forget it, making a game is a lot of work. And even if they share the same direction, there's no guarantee 30 individuals can make a decent game.
As for the actual question, I think the "package" is more important for me than the concept. There are two key questions for: can these people actually pull it of? does the game look fun? If it's well presented, it way well convince me, even if I'm not an adept of the genre.