It's safe to say that Blurred Lines by Robin Thicke as of right now is the biggest song of 2013. Do you think Roar by Katy Perry can snatch it's wig and become the biggest song of 2013?
Obviously Blurred Lines. As much as I despise it, even I can't deny it was the song of the year and it would not be likely for another song to come even close. Anyone would be delusional to say otherwise.