Winning is important, but there are too many things outside the player's control that lead to winning rings. Karl Malone never really had a chance with Utah because he always had either Jordan or Hakeem in his way. Does that make him less great? I don't think so, just unfortunate.
Also, if Jordan had played his entire career with the Bullets, he may not have won any rings. Ownership and front office are pretty important.
Like I said, if we were going to lay ground rules for this list and winning was weighted heavily, then I'd sneak Russell in near the bottom of my list. When I have some time, I want to think about it and redo my list based on winning. That would take some thinking.