Love @Dr Pepper 's version of doing it so i'm stealing and adding:
Best attraction - Austin
Most entertaining - Rock
Best wrestler - HBK
Best "character" - Undertaker
Best "storyteller" - Cena (omg... someone is going to kill me but i swear the guy had money matches and tells a story with pretty much anyone)
Best all around - Jericho
On their way to being immortalized - Daniel Bryan, Flair or Becky (goat woman), Omega.
Realistically there are just too many options. Wrestling has entertainment, in-ring, promos, attraction, etc. There is no definitive answer. I think at the end of the day there are about 10 people who can have an equal share of GOAT.