I think the measure of the 'greatest manager' of all time is not the amount of success he had with his own team, but also how much he has contributed to his own community as well as the BB community.
this could be things such as mentoring, U21/Nat team representation and community involvement, forum discussions.
it could also be tactical and training discovery. statistical collection or analysis of the game engine/training stats, tactics etc.
after saying all that, id like to nominate myself as the greatest of all time LOL