The photo above is a screencap from an unembeddable table at The Huffington Post, documenting that Fox News had the top ten cable news programs for the second quarter of 2009.
The HuffPo article is brief and doesn't delve into the reasons for these results. It would seem to me that one could divide the American public into A) Those Who Watch Lots Of Television, and B) those who don't. According to the data, Those Who Watch Lots Of Television favor "Nickelodeon, Nick at Nite, USA, and TNT" as the top four channels for "total day." They then rely on Fox as their source of news.
Those of us who don't watch lots of television get our news from the internet.