Nvidia as requirement? Where is that stated?
'GeForce' is the answer but you are not seeing it as an answer.
Although we have many so-called manufacturer 'names' saying GeForce, all GeForce cards are manufactured using nVidia graphics chips.
All of the 'GeForce' manufacturers buy at least the chips (or even buy whole cards) and put their own labels on the resulting boards. OEM computer makers do this also.
The features needed by other games have been limited to only supporting certain graphics chips because other chips don't always offer the exact same capabilities. It isn't a game makers fault if the graphics chips from ATI, nVidia, Matrox and S3, etc have incompatibilities, the problem falls to consumers needing to find SOME way to tell card makers to be compatible.
*edit*
Recommended or minimum does not mean that setup listed is all that will, also not always are posts on the forum updated.

I joined intending to only ask if ATI was supported, but fearing the potential wrath of readers (those who could quote chapter and verse about searching), I knew that I'd better research the forum posts. I saw ATI was mentioned for a MacOS post, but I already knew of the hardware post that said GeForce 2 was the minimum. My history at TechIMO and at USALug says ATI is not GeForce, so I needed the clarify whether the
minimums had changed since your helpful hardware post was made.
That is a great way to start out (to have the minimums posted), so naturally I wanted to suggest to someone that if the minimums had changed, please maintain that helpful post.
The game does work on ati cards and many people play ps on them.
And a 64 bit version too, I see. Maybe I get to play after all?!