Based on what I've heard, it appears that EA Montreal (the team behind the current-gen NHL games) was under pressure from EA to purposely not improve the game because the company wanted the 360 version to be the premiere version of the game.
If you ask me, I think EA has had right analog stick control of the hockey stick in the works for a long time, and once they development of the 360 version began, they decided to make it exclusive to next-gen.