Hmm...
If I had to choose, I'd pick Britney Spears over Lady Gaga. Nothing personal against Gaga, yet I "grew up" with Britney. I guess the only way to determine Gaga's impact is if she'll stick like Madonna and Britney did. I have confidence she will.
Everyone needs to play Lost Odyssey! Any opposition to this and I will have to just say, "If it's a fight you want, you got it!"