Okay, yes, there may be more examples from the past that we can point to as mainstream artists who were actually good, but that's kind of the hindsight is 20/20 argument. In thirty years there will be current mainstream artists that will be praised and held up as examples of how great music was in the 200x's / teens, but those artists will be greatly in the minority, as they always have been, to the total number of recording artist.
Since others are listing some of their favs I'll do the same
The New Pornographers / AC Newman
The Flaming Lips
Animal Collective (some)
I doubt that. Many of the successful pop artists of the early 2000's are already forgotten.
Maybe it's because there are no more big revolutions in music, almost everything that is thinkable has already been done.