Well, in the strictest sense, he is not a "Greek" but a western Father (Alexandrian), but I will agree that he had many things in common with the 16th century Protestants.
His remains celebrated in the Church both east and west, solely because of his stance an Arianism. The Church is willing to shove all his other "Protestant" characteristics aside -- instigating riots, and forcefeeding his views to the peope.
He was certainly "Protestant" in insisting that what matters is not theology (yet he was the one who used force and every other means to shove his down everyone throat) but salvation.
More importantly, his view of the OT is not what the Church as a whole accepted, although his canon is what the Church pretty much finalized as catholic (universal).
That's important, because the Church operates on the basis of the consensus and not individual truisms, as is the case among Protestants.
Athanasius of Alexandria (Greek: ÁèáíÜóéïò) (also spelled "Athanasios") (c.293 May 2, 373) was a Christian bishop, the Bishop of Alexandria, in the fourth century. He is revered as a saint by the Roman Catholic Church, the Eastern Orthodox Church, and the Oriental Orthodox Church, and regarded as a great leader of the Church by Protestants. Roman Catholics have declared him, earliest living, one of 33 Doctors of the Church, and he is counted as one of the four Great Doctors of the Eastern Church.
http://en.wikipedia.org/wiki/Athanasius_of_Alexandria
Those fathers who wrote in Latin are called the Latin (Church) Fathers, and those who wrote in Greek the Greek (Church) Fathers. Famous Latin Fathers include the Montanist Tertullian, St. Augustine of Hippo, St. Ambrose of Milan, and St. Jerome; famous Greek Fathers include St. Irenaeus of Lyons (whose work has survived only in Latin translation), Clement of Alexandria, the heterodox Origen, St. Athanasius of Alexandria, St. John Chrysostom, and the Three Cappadocian Fathers. http://en.wikipedia.org/wiki/Church_Fathers
And where does it say that he is celebrated solely because of his stance on the Trinity?