MSNBC is the negative output. While Fox News is on top. Before you start throwing insults and ignorant comments about Fox News, look... Glenn Beck, Don Imus, Lou Dobbs, three of the big newscasters switched to Fox News because where they were before was not making them comfortable. They chose to switch to Fox News.
Wait, lets just get this straight. While its okay for Fox News, and much of the News Corporation holdings to lean to the right, it is totally unacceptable for MSNBC and NBC Universal to lean toward the left? That doesn't make a whole lot of sense, especially if everything is supposed to be fair and equal in the media. Truth of the matter is that in all forms of media, journalists across the board, even at "Conservative" publications, tend to lean to the left. Oh noes! Its the end of the world!
Regardless of that issue, the figureheads that you mention there are at Fox News for the money, simply put. Imus and Dobbs were never all that popular to begin with, so I'm not sure where you're getting that from, but certainly their own political and social views fit in a bit more comfortably at the house of Ailes and Murdoch.
The big late night show host Connan O'Brian has already switched to Fox from NBC. Bringing down MSNBC/ NBC, hurting them a lot now.
If you read things on the internet carefully, Conan isn't going anywhere but out of the chair at the Tonight Show. There is an extreme likelihood that there will be a non-compete clause in his contract that will keep him off television for a while, but that means little in a world where the media is controlled by just a few corporations. Conan
could go to Fox, or he could do something entirely different.
All of that has very little to do with the standing of NBC Universal, but more about their inability to provide decent primetime programming that can carry viewers into the local news, and then, onto the Tonight Show and the Late Night Show, and so on.