I checked the internet a bit and it seems like there are emulators for those, but I don't think they work too well in games. According to a forum I read they got a leaked alpha of Doom 3 to work on a GeForce 2 card by using NVemulator. Without the program D3 didn't work.
hmmm, never heard to nvemulator, either way like the 3dfx emulators it'll be a real processor hog, its not gonna make for playable frame rates in my opinion if there is such a thing anyway