I think we're talking about a combination of things:
- Inspiration. How many new games were coming out; coming out with new, different ways to play, and just plain playability. I happen to believe that the more "abstract" the game, the more interesting the play.
- Popularity. Not just of certain games or genres, but also of the arcades themselves. Not only does the "Golden Age" fit in well with this, but also the silver age with the development of the fighting games.
- Importance of the Arcade. As a teenager during the "Golden Age," I know for sure that the arcade was king then. Even during the Silver Age, all the good games first came out in the Arcade, then were ported to video systems.
Not that important, innovative or interesting games have not come out during the Dark Age, or even this Tinfoil Age (I prefer Sunset Age, but the board has spoken). However, I do believe that whatever happens now happens in the home console market, with the Arcade market being more for "games" requiring a more ... viseral response (drumming games, boxing games that require you do some actual punching, dancing games, etc.).