If you don't have Comscore, check out the Alexa data below, which tells a similar story. I've split the charts into pageviews, time spent, and reach. Facebook wins by a long margin on time spent, but the race is much closer on reach and pageviews according to Alexa. Facebook is the blue line, Google is red, and Twitter is green.
Twitter is still a long way behind, except on time spent, where it is close behind Google.
This first chart is reach. Google is ahead.
This second chart is time spent. Facebook is ahead.
The third chart is pageviews. Google and Facebook are fighting to the death, switching positions over and over again.