Easily both. It is really hard to choose, as each one has its own merits. Moreover, since the inception of 3D, 2D has become a genre all its own, so choosing the former over the latter is kind of silly, in my opinion. I just can't seem to apply a "versus" between them anymore. Not to mention the majority of my favorite fighting games are in 2D, and I'd be devastated if they made the transition over to 3D, as it would never be the same.