I think it's technically feasible, but a fair chunk of work, especially if you want wide compatibility (either presenting the same hardware interface as a real

I think it's technically feasible, but a fair chunk of work, especially if you want wide compatibility (either presenting the same hardware interface as a real card, no doubt with lots of reverse engineering to do or doing your own interface and writing a DX driver for it and then testing it across lots of games). It's also not going to be cheap, on top of the FPGA you'll want a PCB and support chips. Charging a few hundred dollars for retro hardware replacements is feasible but for now at least actual retro 3D cards can be had for less money. So an interesting project, but I don't think we've reached the point it's interesting enough for someone to attempt. I think there's far more interest in FPGA replication of full consoles right now (check out the MiSTer project https://github.com/MiSTer-devel https://github.com/MiSTer-devel). There's lots of excitement around the upcoming PSX and Saturn cores for that. I suspect a Voodoo/GeForce replica would be a similar amount of work but far fewer people interested in having it.