That... is some seriously flawed logic. Just because you can name a successful system that has variants with different fluff, that doesn't mean that all fluff is the ruling factor for games. I have personally played 20+ game systems over the years. I always picked my game system by what seemed to have an interesting setting. Many times, this was a huge mistake because the awesome setting was attached to an awful game system. In the end, I started taking good settings and putting them on top of other game systems to create a tolerable game. You can make the fluff whatever you want, but an awful game system is an awful game system, and when it comes down to it... The game mechanic is what makes the game exciting or not. You can use the exact same explanation and setting on top of different games, and the excitement and fun level will vary. Hell, you could just have it be a storytelling game. Would that have tons of great fluff? Yep. Would it be a fun game? Not really. Superhero posing/emoting is dull as hell.