Overcoming years of (deserved) repressed guilt, a terrible upbringing, years of service to an abusive master, etc etc in order to save a loved one and thereby killing the Sith Lord who had masterminded a galactic war and subsequently held the galaxy under his power is undeniably great. You can’t measure Anakin without taking the end of ROTJ into consideration.

But anyway, discovering how to be one with the Force after death such that somehow you can manifest as an individual ghost is a pretty big deal so maybe it should be Qui-Gon.