ofcourse they were. 3dfx had superior designs in a lotta aspects.

they may not have had the performance crown at the time of their demise, but their image quality was far better then that of nVidia.

And if I remember correctly, 3DFX was, and still is the only company that had hardware FSAA.

I think I read somewhere that FSAA is done by shaders and all that stuff by nVidia and ATI, but with the T-buffer, 3DFX was the only one that had hardware rendered FSAA, is that correct??

Yes Exactly, nVidia had Ordered Grid Super-Sampling  FSAA mode which was indeedly far less detailed qua image quallity that Rotated Grid Multi Sample FSAA which 3dfx utilized