Archseer

While there is no specific, binding definition for when this title is bestowed, it is generally understood it is only official when recognized by the The Wizards Guild, and it only granted to wizards truly worthy of its reptuation.
Only the most powerful wizards those who at one point or another might have been called "First Among Equals" are called Archseers, and when the most powerful wizard at any given time still doesn't stand enough apart, they will not be given the title.