Otto Von Herunterhängen
I don't think there is any "main stream" anymore. I mean the days of top 40 and record companies colluding with radio stations to push artists is pretty much over. I never was a top 40 person anyway, it's always sucked.
There is a whole lot more variety these days.
And since I've always been into music that other people find strange I'm loving it.
But seriously, the last of the "main stream" bands were from the 1990's. I can't think of a single one that has domineered since then. There are plenty of new ones out there, and they are good, don't get me wrong. But they are all fighting for attention.