I still say Virtua Fighter 2 is the best 3D beat 'em up ever.
8 years on, and we can still fire up VF2 and be amazed by the graphics. Not from a 'wow that looks realistic' standpoint of course, but seeing the humble Saturn run a game in such a high resolution, with such detail and accuracy the arcade original, and best of all, seeing it all run in 60 fps, just brings a tear to the eye.
And on top of that, it's one of the deepest fighters ever made, with a vast amount of *real* moves, all of which can be performed so elequently and mastered to hell until you can perform them blindfolded, and yet there's still room for improvment... it just shows the world what the Saturn could really do.