Firstly, the game wasn't trying in anyway to take itself seriously. It was a cheesy action game and it reveled in it. And, Bayonetta is currently my vote for game of the year.
And, according to MovieBob of this site, Bayonetta is perhaps the first video game female character to forgo the dismissive and submissive conventions of a female character. Bayonetta is the "first video game women that's been successfully and unashamedly built to not just be sexy, not just be strong, but to be sexually intimidating." Check out the videos for his complete thoughts.
I agree with very much of what MovieBob had to say; I'm sure Bayonetta isn't the absolute first, but probably the first that has such a level of popularity. Bayonetta is a very strong character in every sense. She does do some very sexual dancing and moves in the game but she does it because she wants to (it fits her character), she enjoys doing it, and it's not just to attract male gamers to buy the game like Dead or Alive.