Don't know, this time the battle will be quite significant. Sales wise, product success wise, NVIDIA's even number product line has always traditionally equaled ATI.
For example: GeForce1 - First DX7 architecture, no real competitor
GeForce2 - Was ultimately more successful than ATI Radeon, even though Radeon had better features...
GeForce3 vs. Radeon 8500 - Was a tough battle, but again NVIDIA won due to better drivers.
GeForce4 Ti - Runaway success....
GeForce FX - Runaway failure...But it fought well till the 6600 was released.
GeForce 6 - Like GeForce2, sales wise they became the winner as compared to ATI, even if they didn't have the fastest card on Earth (for example, Radeon X850XT PE is faster than 6800U)
GeForce 7 - Tough battle, win some, lose some....Lots of IQ problems, bugs, no angle independent AF
GeForce 8 - I can only hope it repeats the success of the GeForce 2, 4 and 6 series...This looks like some sort of blessing, every 2 generations NVIDIA ultimtely wins the war, whether in terms of sales or in terms of performance.
But logically speaking, this time around NVIDIA has had the DX10 hardware for quite a while now, they have had plenty of time to prepare themselves for ATI's offering, there may even be an 8800 Ultra or 8900 in the works, but maybe this generation, like the 6 series, will end with NVIDIA getting better sales despite not having the fastest card on Earth....