Before the Great Schism there were five patriarchs: Jerusalem, Alexandria, Antioch, Constantinople, and Rome. They were considered co-equal leaders of the Church. Rome was not "more equal" than the rest...they shared in the leadership of the Church. It was only with the growing political power of Rome, and the Roman patriarch, that the patriarch of Rome began to believe that he was the supreme patriarch. There is no justification in Scripture for this, and the Orthodox Church (represented by the other four patriarchs) resented his usurpation of power.
Therefore, the Orthodox Church has no problem denying the supremacy of the Pope...he is the one that broke fellowship with the other four, not the other way around.
It is late, and I don't intend to go any further right now. I hope you receive this in the spirit in which I have intended it - as mere explanation, and not condemnation.
grace and peace to you