'The Voice' tops 'The X Factor' in ratings war

Two rival singing competition shows went head-to-head last night, but only one could win. And even the star power of Britney Spears on Season 2's premiere of "The X Factor" was not enough to overcome the draw of NBC's rival show -- and rival pop diva Christina Aguilera -- on "The Voice."

According to preliminary Nielsen ratings, an average 8.5 million Americans tuned in to watch Spears and singer Demi Lovato's debut, alongside Simon Cowell and L.A. Reid. The episode dropped about 3.5 million viewers from the show's 2011 opener, which is surprising given the aggressive publicity by Spears and Cowell. Spears reportedly earned $15 million to do the show.

See Britney dishing out tough critiques:

As for "The Voice," 10.7 million watched a third episode Wednesday.

Cowell can't be pleased.

Last week, he slammed NBC execs for using "dirty tricks" to steal his viewers. NBC was originally planning to air "The Voice" on Monday and Tuesday but changed course at the last minute, adding a third show to face off against "X Factor." "I think of it as kind of a gentleman's agreement, but you have to rely that the viewers will make the right selection," Cowell seethed to TMZ. "I think three nights in a row [for 'The Voice'] is too much."

So why did "The Voice" triumph?

One possible reason is that people who watched the show on Monday and Tuesday probably wanted to continue to see how things unfolded Wednesday.

Watch Wednesday's episode of "The Voice":

There is some good news for "The X Factor": According to social TV analytics firm Bluefin Labs, the show prompted about 1.4 million comments on Twitter, Facebook, and other social media platforms on Wednesday, making it the most social season premiere of all time.