As previously mentioned feature sets are not as important... say if ps4 was capable of 100% photoreal gphx, but with most of it being programmable and few features... you wouldn't be comparing it to a voodoo2 now would you?
No but i' be comparing it to whatever chip is out at the same time. And if that chip could do it all in hardware(which would be much easier to implment and code for) or even some of it in hardware then yes i would compare them . Now if the ps3s gs has the same feature set as the voodoo3 but offered 10000 times its fillrate i would still compare it to the voodoo3. Since the onlyadvantage it would have is fillrate .