Well, 2D fighters (as in 1v1 fighting games, of course) are generally really high investment ticket items, as is JRPGs when it comes to professionally made stuff. In those cases, those games will definitely still be in the mainstream. (i.e. Street Fighter, BlazeBlu, Final Fantasy, etc) platformers are now the new indie favorite though. If you look on say, reddit r/gamedev, for example, half of the new projects that get a showcase thread are platformers.
Shumps might be niche now, but there is really no shortage of places to go to find new content. Especially in the Japanese circles. Seriously, those guys have to be a little masochistic to play the shumps that they play. Communities for those certainly exist too.
Puzzle games are fair though. Those have been eaten up by the facebook / mobile gaming market, and while they are incredibly popular, the audience there are not the type to go out to find communities to talk about them in depth.
Music games I have no idea. Seems like all the music games I see are just excuses to move peripherals.