The YouTube analytics company ChannelMeter
sent over this chart, which covers the song/video's meteoric rise. Granted its main competitors are much older -- and this chart only shows more recent months, long after their views decelerated -- but... If Gangnam Style keeps up its current velocity, it's going to pass J.Lo's "On the Floor" within a week and then Bieber by Thanksgiving, hitting one billion in December of this year.
Of course, it is a fad, so that pretty graph could change in a New York minute (or Seoul second, as it were).