The Orthodox argument on the Papacy is that all the Patriachs are equal (the Pope is the Patriarch of the Latin Church). They believe that the Pope has only a “primacy of honor” and they do not believe in Papal Supremacy.
I hope the Orthodox will fly over hear and present somemore info to you.
The Protestant argument varies among denominations. Some believe that, as the Orthodox do, that an Ecumenical Council has final say. Others believe that the Scriptures are final witness.
You will have to ask the Protestants individually.
But, anyways, I believe that both opinions are contrary to the testimony of the Fathers and the Scriptures bear witness.
