It's really hard not to go with Bird. The guy just did so many things well. The most impressive thing about him though was his ability to see the game unfold. There are so few players who can actually do that, at least to the extent that he could. When you combine that quality with the ability to score, rebound, and pass the way he could you have a very special player.
Beyond Bird and other C's players like McHale, I would have to say maybe Scottie Pippen. He reminded me of Bird in ways in his ability to dominate in so many different areas of the game. He wasn't as much of a cerebral player by any stetch but still he was one of the better individual defenders the league has seen in a while. I always said he was for several season the second best player in the game and while he benefitted greatly from playig with MJ it was certainly a reciprocal relationship.