Driven by a flurry of big breaking-news events in 2011 – everything from the Japanese tsunami to the Egyptian uprising – Time (NYSE: TWX) Warner-owned CNN Digital averaged 73 million unique viewers a month last year across its various platforms, according to comScore (NSDQ: SCOR). Fox News Channel, far and away the leading cable news outlet in prime time, averaged less than 30 million unique users across its channels, while No. 2 network MSNBC (NSDQ: CMCSA) averaged just over 50 million.

Given that other Time Warner sites including Time.com and People.com are folded into the CNN Networks metric, just comparing unique users overstates CNN’s advantage. But in the social networking universe, the 1 million fans on CNN’s Facebook page dwarf those for Fox News by a factor of eight. And with a combined total of 9.4 million followers, @CNN and the rest of the news brand’s Twitter handles have 1.8 million more followers than the closest news competitor, the New York Times.

CNN.com served up 135.9 million page views last March when the earthquake and tsunami ravaged the Japanese coastline, and it averaged 101.3 million video starts a month, a 19 percent uptick over 2010. Sections including Belief (up 64 percent to 7.8 million page views), World (up 23 percent) and This Just In (up 29 percent) also posted big gains.

CNN Digital also remained No. 1 in mobile news for a fourth straight year, averaging 19.4 million unique users, a 60 percent edge over Fox News Digital. (For its part, Fox News is quick to note that it has an engagement metric advantage – according to comScore, the average user spent 10.7 minutes on Fox News sites compared to just 2.2 minutes for CNN.)

These digital rankings, of course, are a complete reversal from what has been happening on cable news television over the last decade.

The Atlanta-based CNN ranked No. 3 in prime-time cable news ratings last year—despite its 16 percent uptick in average nightly prime-time viewers and Fox News Channel’s 9 percent decline. For the year, Fox averaged 2.2 million watchers in prime time, MSNBC came in second averaging 902,000, followed by CNN with 735,000. This, according to TV ratings tracker Nielsen.

Perhaps most key, CNN trailed Fox in the all-important adults 25-54 viewer demographic, averaging less than half of Fox’s 522,000 in the category in which advertising sales are based on. So what’s with the discrepancy between digital and cable performances?