I wouldn't include the 9800 GTX in your list. It was a slightly cheaper, rebranded 8800 GTS 512 card.
The 8800 GTS 512 and 9800 GTX were on par with the 8800GTX. The top end 9 series from Nvidia was just basically a rebrand top end 8800 series. I think it was the most stagnant of all generational changes in my GPU history that I can remember.
I know but I put it in there for the sake of completion. At least I didn't use the 9800 GTX+ or GTS 250 re-branding!
IIRC, there actually was a small difference between the 8800 GTX and 9800 GTX but I think that it was mostly the fact that the 9000-series was PCI-Express v2.0 while the 8000-series was PCI-Express v1.x. The stagnation at the time was because the 8800 GTX just annihilated the HD 2900 XT and was even faster than the HD 3870. There wouldn't be serious competition from ATi until they fixed the TeraScale architecture with HD 4000-series. That's when the HD 4870x2 knocked the GTX 280 off of its perch as the fastest card in the world. Jensen had just sat back and let his R&D department work its butt off to have their next product ready and waiting for ATi's response while just refreshing the G80 to the G92 with the new interface.
That's why nVidia was able to react so quickly to the HD 4870x2 with the GTX 295. I think that nVidia expected to keep one step ahead of ATi in this way. However, just like ATi flubbed early TeraScale at the worst possible time, when nVidia had created the G80, nVidia flubbed the GF100 at the worst possible time. This is because ATi released their Evergreen HD 5000-series and it just obliterated everything that nVidia had at the time.
Guru3D's Hilbert Hagedoorn's review of the Radeon HD 5970 (code name Hemlock) had the funniest paragraph that I've ever read in a tech review. I actually laughed my butt off reading his article because I'd never seen someone say something like this before (or since for that matter) in a tech review:
"(Tom Clancy's) HAWX is very lenient towards ATI cards thanks to DX10.1, but with so much brute power, NVIDIA has been working nervously to optimize their drivers. And as such the more recent drivers make the GeForce cards much more competitive. As such the GTX 295 pushes 42 FPS at 2560x1600 with 4xAA (on average), but the Radeon HD 5970 brutally sodomizes the GTX 295 here with nearly doubled up performance."
Let me help you with the imagery...
EVGA GeForce GTX 295 before the HD 5970:
GTX 295 after
the HD 5970 had done its "brutal giving of the sword":
"Yes, it's childish and stupid, but then, so is high school!"
- Ferris Bueller, 1986