I still remember when a 7800GTX was a beast of a card. Also the 8800 GTX and Ultra was legendary
I don't think the GeForce 7800, for the most part, was all that great. The GeForce 6 series it replaced was much better in it's time. ATI was much better off around the GeForce 7 series. With the GeForce 6 series, the GeForce 6800 Ultra fell in and made nVidia's own previous GeForce 5950 and even the Radeon 9800 look silly, and the lesser GeForce 6800 GT (same thing underclocked) was even cheaper and really popular. I remember back in 2004 on these forums when it was
the card to have, and I wanted one so badly and seemingly everyone here had one, but my GeForce 4 Ti 4200 had to do, and do it did (I actually had a GeForce 4 MX 440 w/AGP8x at the time that performed closer to a GeForce 4 MX420). I mostly did emulation then (and had just a Pentium III 800MHz anyway...), but I wanted to try OpenGL 2. When I got my GeForce 6800 GS AGP and got more into modern (at the time) PC gaming, it was rather magical though. Far Cry, Doom 3, OpenGL 2, and more... those days were just magical.
As for the GeForce 8800 Ultra, it was a joke. It was just an overclocked GeForce 8800 GTX (which itself was great), and it was more expensive and late to the party. With the GeForce 8800 GT being half the price of the GeForce 8800 GTX (let alone the Ultra), but almost as good in most cases... it destroyed the merit, but then again, the GeForce 8800 GT was a rare card, like the GeForce 4 Ti 4200. I'm proud to have owned both (can't say I own both anymore; the former was given to someone here).
I had a GeForce 4 MX 440 w/AGP8x, GeForce 4 Ti 4200 w/AGP8x, GeForce 6800 GS AGP, GeForce 8600 GTS OC, GeForce 8800 GT OC, and now a GeForce GTX 560 Ti. In that time span, I had but on ATI card, and it was some sort of Radeon 9700 or Radeon 9800 (can't remember which, exactly).
The Radeon X1550 I bought for my parents since the Intel IGP's drivers kept crashing under Vista was good though, and actually works flawlessly to this day for them under Windows 7. I prefer nVidia, although that's half a subjective choice. My favorite has to be the GeForce 6800 GS AGP. Far Cry was amazing. Now, the games to need such GPUs seem to be smaller (what, with all the console ports), and I'm back to how I was in my GeForce 4 Ti 4200 days just playing a set of games that don't need the latest and greatest, so I'm set. Choosing now though, I'd go nVidia still.