It is already over saturated, which means soon only a handful of companies will be making any real money from FGs. Those being Namco and Capcom. Japan has a plethora of 2d fighters it releases every year, whose going to play them; especially at this astounding rate of production?
FGs are different from FPS in that you actually need to invest some serious time to get good at them...you can't just pick them up and play. Or at least I can't. Because they're quick to pick up, follow a story, get online and play...FPS have more longevity and are better investment. Many of the FGs these guys buy they only play for a couple of months, and realize they don't really care for the game.
To me that's a waste of money. It's SC and Tekken for me.
If you paid attention you would realize that they're only a handful of players that are serious about FGs. In comparison with other gaming genres, I feel the FG community on average gets less newcomers, especially to the competitive scene. More than likely if a member is new to an FG he already plays another one in a different community.
Basically we just share players.