It depends on what time scale you look at. Recently it's been b4b, but a decade back ATI was often beating nvidia and then back again as cards like the Radeon 9700 came out.
I miss those days, although I prefer the power of today's cards more.
The Jedi Master
It's closer than the 9xxx series, Nvidia didn't have an answer for the 5870 till 6 months after its release, same with the 7970, and even with that they had the GHz edition ready to answer to the 680.
