You got some 'splainin to do
nVidia made huge leaps ahead in graphics card technology when they were the underdog and 3dfx was king of the hill. they pushed hard and outclassed the 3dfx cards in every possible way, resulting in bankruptcy of the one-time giant. ATI was not heavily into gaming cards and was more concentrated on OEM licenses and their all in wonder series for enthusiasts.
Fast forward a few years....
nVidia pushes their technology ahead, but being the top dog doesn't really make any giant strides. Sure there were some nice new features along the way: faster memory, ramped up core speeds, smaller die processes, inclusion of hardware T&L, etc. However, they haven't really pushed the envelope as much as they could.
ATI, on the other hand, steps up and enters the gaming market. The Canadian manufacturer produces the Radeon, which at inception was no GeForce killer. As such, nVidia didn't take them too seriously. Suddenly ATI produces the card that obliterates the GeForce: the 9700 Pro. It surpasses the Ti4600 in virtually every single benchmark, and the bells and whistles it provides proceed to decimate the ti's remains. Things like 16x anistropic filtering that barely cause any performance issues, yet make images far smoother than anything nVidia can produce, are just the icing on the cake.
In reaction to this, nVidia promises it's new architecture will recapture the crown. Unfortunately the benchmarks prove differently. The new nVidia cards offer some improvements, but overall they are not the Radeon-killers they were supposed to be.
Now, ATI prepares to kick the nVidia cards around even more with the 9800. If history is a teacher, nVidia had better have something incredible in the pipeline, or it may be disasterous for them. 3dfx went out of business because of the technological leaps of nVidia. AMD is poised to file bankruptcy if it can't get back into contention against the Intel processors. Now, ATI is looking to smash nVidia into oblivion. I'd wager that if nVidia hasn't gotten back into the game by Q4, they're gonna be seriously hurting.