I like GaGa and there sure is a lot of buzz about her right now, but pop culture can make you a queen one day and than you fall like a rock (see Christina Aguilera).
The other big girls today have had their moments and have stabilized since then. I mainly mean Britney, Pink and Beyonce. They might get less buzz than GaGa, but they are doing their thing and have lasted in the game for a decade. In 3-4 years (2 more album eras) I'll be able to tell if GaGa's gonna stabilize or not. Right now I'm not sure. She's a good business woman though and will try to do everything to maintain her success, it won't be easy though.
Tik Tok would have had much more impact if Ke$ha agreed to selling it to McDonald's.
I agree that it was huge (Simpsons intro anyone?), but can you really compare it to the success/impact of Poker Face or Bad Romance?
Vs. 
