http://www.youtube.com/user/theyearinreview?feature=etp-pt-rew
Number 1
PSY Gangnam Style
http://www.youtube.com/watch?v=9bZkp7q19f0
One billion views in six months
Uploaded June 2012
Number 2
Somebody that I used to know
http://www.youtube.com/watch?v=d9NF2edxy-M
142 million views
uploaded January 2012