Viewers are “Keeping Up with the Kardashians,” making the E! series’ Feb. 21 showing the top-rated non-sports program on ad-supported cable among adults 18-49 (whew! Could there be any more qualifiers there?!) in first quarter 2010.

Several basic cable nets had reason once again to crow in 1st quarter 2010, as their flurry of press releases today seemed to indicate.

Here’s a round-up of PR headlines:

USA’S 1Q Marks 15th Straight Quarterly Win – The Longest Winning Streak Ever

Nickelodeon Scores Its Most-Watched Quarter Ever; Tops Basic Cable with Kids, Tweens and Total Viewers

A&E Finishes Best Quarter In Network History Ranking As the #4 Entertainment Network In Cable

ABC Family Delivers Its 2nd-Most-Watched Quarter of All Time in 1Q10 in Key Demos

E!, Style and G4 Post Record Numbers for First Quarter and March 2010

History™ Posts Best Quarter In Network History

Oxygen Marks Best, Youngest Quarter Ever

Investigation Discovery, Science Channel and Military Channel Each Score Best Rated Quarter Ever

Spin winner goes to History™, only because they’ve actually found a way to trademark the word “history.” Plus, as a result, they managed to get the word “history” in the headline twice.

A roundup of ratings, via Turner’s research department. First quarter stretches from Dec. 28, 2009 to March 28, 2010:

Persons2plusqtr1 Adults1849qtr1