I dunno what you want to see that way:
I'll take a few VGA captures in Quake III.
All your screen shots show banding just as bad as each other, in the case of the Kyro and Geforce they are pretty indistinguishable, and to the naked eye (without zooming in on the image to observe the compression artefacts) I doubt anyone could tell the difference between the Voodoo and Kyro/Geforce.
Phils VGA captures should be WORSE that direct framebuffer grabs (which I'm assuming you provided), due to *possible* signal degradation through the VGA cable, yet image analysis on his screen shots show 0 banding or compression artefacts, so I don't think there are any IQ issues with the Geforce2 GTS (or VGA bandwidth at that res). o.0
While the renderer may have used uncompressed textures, when you saved the resultant-screen shot/frame-grab, you then saved the image in jpg and not at 100% quality, ergo it saved it in a lossy format (reduced quality for compression) and this is the banding issues seen in your images, not bad IQ from any GeForce 1-7.
Of course the size of the images suggest this. Phil's 1600x1200 image is 4.28MB, and your 1600x1200 images are 730-750 KB, so they are obviously compressed and that amount of compression implies a lossy one. Avoid JPG when IQ is important, you can't get better then lossless PNG 😀