Hoo boy. I'm unsure, really. As much as I want to say Pearl Jam, I can't say it in confidence with some of their studio works that had been released early in the decade (Riot Act).
I'd go with Arcade Fire. It's been quite some time since I've been so impressed with a new group. To add to that, though I haven't seen them, their live performances seem to be quite good.
I'm really quite fond of some others that have already been picked as well, namely Metric and Radiohead.