These guys sound exactly like stellastarr, who aren't exactly burning up the charts either.
Guitar-based bands that don't tread the Nickelback track just aren't considered mainstream right now. I mean, when I listen to Against Me's New Wave, it amazes me that these aren't radio hits, as they sound like perfect FM gems. And the new She & Him album seems like it fits into the perfect Starbucks/Norah genre that embraces nice sounding music made by good-looking people. It's not a great album by any stretch but it's catchy, friendly and warm.
I'm also amazed that bands like MGMT and Cut Copy are still so obscure, since they are making catchy pop that isn't too Euro, a la Hot Chip, Phoenix, etc.
But Walk's question of, what is mainstream radio is a good one. I don't even know what current music gets played any more, but I suspect it's in the R&B line of things. I know that NPR Music is spotlighting more of the music that the board is into, but that's web-based, not terrestrial radio.