I've only ever played MW2, Black Ops and MW3. I enjoyed MW2, Black Ops was junk, and MW3 I really couldn't get into, simply because I had it on the ps3 and I have terrible aim with controllers.
I enjoy shooters, and MW2 was really my first time playing a multiplayer shooter. Getting a bunch of friends together and tearing it up on Highrise (or not.. you know, we had our days), was an utter blast. So yeah, I did enjoy the series once. But at this point I'm confidently saying I have no interest in purchasing anything else in the franchise. Heck, after Black Ops I swore off the series, until I was unfortunately coerced back in to buying MW3.
Regardless though, I am shocked and extremely thrilled to see a female in the franchise, and honestly, knowing how successful the games have been with their current formula, the fact they made an inclusion like this really gets some respect from me. But still, it's just one character, and heck, most multiplayer shooters could easily have had female counterparts by now. (Brink, why did you fail me?)
It's a good step though. I got just so tired of looking at those manly gloved hands when I played MW2.