First, I need to ask whether a coach for u is the same as a trainer, teacher etc.?
For the western world I believe that the understanding of a "coach" have changed with the management-concepts in businesslife, where "coachING" has been the new hype for some years now! This means that the sportscoach and coaching, seems to coorelate as something very different from a trainer.
If u r looking for a "normative" definition, that is, telling what is a superior coach, it should be different for different cultures, or u should make it so general that it becomes completely uselees!
For a trainer in DK my definition of a superior trainer is a movie (sometimes words is not good enough):
PS: "DONT TRY THIS AT HOME"
http://www.youtube.com/watch?v=DmNyv2Pddg4&feature=related
YAWP