I think Moderner Warfare was a very unenjoyable game based on my playthrough of the campaign and my thoughts as a gamer, so I never bothered with the multiplayer. I also made sure to borrow a copy for my 360 and even made sure I wasn't signed in to MY gamer profile, so as not to stain my gaming record.
But, I guarantee it'll sell just as well as Moderner Warfare.
Why? 'Cause bros love them some moderner warfare and, let's face it, they'll pay $60 for anything shiny you hold in front of them (new Madden game every year, anyone?).