Actually, screw the open-source gaming scene. It's all about indie games now, and it has been for a while. The open-source scene has just been riding on the coattails of commercial games for years, with only a handful of exceptions, like Tremulous. And now even Tremulous is aging unpleasantly.
Case in point: In 2003, an indie company named BraveTree threw together a small, cheap game called ThinkTanks in half a year. Instead of being Yet Another FPS, it set itself up as a third-person tank-combat game (like BZFlag, except in third person), with heavily different gameplay and cartoonish aesthetics (this was years before TF2). Something clicked with quite a few people, and it quickly gathered a surprisingly large community. Of course, when BraveTree was bought out, their parent company (GarageGames) pretty much gave up on it (no new releases since), but the community kept it going, even replacing the master server when it was discontinued.
Of course, without GarageGames's support, they're off even worse than Tremulous is right now (about 20 active players). But that's just one obscure example. We all know about wall-walking, right? Prey made it a main point in its gameplay before 1.1 came out (IIRC), plus other inventive stuff. Between those two games, I'd say that's more innovation than the whole open-source gaming community's come up with so far. Indie developers are motivated by money, meaning they have an incentive to do something new, but not to the point that they have to aim for the least common denominator. It's the perfect balance- they're coming up with new ideas while we're squabbling over where the sounds for 1.2 should come from.
And don't get me started on Valve.
