A couple suggestions from a budding graphics programmer
I've been watching the Big Four compete with their different technologies for some time now. nVidia (who also may be using some technologies from 3dfx, whom they acquired in 2000) produce really fast cards, high clock cycle speeds, and so on. ATI produces (from what I have seen) robust technologies which lack in speed and driver support (heard LOTS about their flaky drivers).
But there are 2 technologies that may yet overtake the above two, in terms of superior graphics technology; only problem is they are only evolving now into something that could eventually be "Big". And the reason they may pull this off is because they provide intelligent technologies.
Matrox's new Parhelia GPU is scary... lifelike graphics from a mediocre model, given a texture for color, a texture for bump, and a texture for polygon interpolation from the original. Take a look at http://matrox.com/mga/products/parhelia512/technology/disp_map.cfm, they have amazing demos there. The main reason why this card will rock? Less bandwidth usage for textures and polygon data (and less of a need for blazing fast RAM when there's not as much data to push across the bus).
And PowerVR produces probably the most intelligent cards out there; problem is that their GPUs are not up to snuff in terms of capabilities and programmability. http://www.powervr.com dictates that the fastest card is the one that only renders what is seen... and they do the best job of the listed 4 technologies here, in terms of hidden surface removal.
Right now, the best graphics card to buy is one which (a) has a programmable GPU, because this means it's more than just a "purchase", it's more like an "investment", where for months and years to come, more and more games will take advantage of their capabilities. (Currently, few do. Doom 3, and that's about it.) And ( that has crisp, clear rendering without a lot of washed out image quality. Take any game, max out the graphics, and see which technology shows up best... and which one scrambles faster to make sure that the drivers work properly. This is your best choice.
(Of course you could be like me, and hold out with your Voodoo3 because you're too damn bullheaded to buy an nVidia card, and too damn poor to buy an ATI! )
