In my view, the best UX designer is one whose efforts are never noticed.  It's my job to create elegant solutions which clear the path between the player and the visions of the game designer.  I loathe official “tutorial” like learning, which takes players out of the experience and postpones play.  Instead, I espouse the “learn-by-doing” design mentality.  It’s my belief that the strongest experience comes from a very close collaboration between game and interaction designers.