The Church of Rome's primacy is based on the City of Rome having been the capital of the Roman Empire.
I've heard this said quiet a bit, and not here to argue the point necessarily, but didn't the early fathers base the primacy of Rome on the Martyrdom of Sts. Peter and Paul?
How early is early?
It's been a while since I read Dvornik's Byzantium and the Roman Primacy
, I don't have a copy, and I don't know if there's better scholarship out there since it was published, but according to my recollection, he claims that the "apostolicity" of Sees was not really an emphasis until about the fifth century. No one denied the martyrdom of SS Peter and Paul in Rome, but it wasn't evidence in support of primacy until the ascendancy of Constantinople.
That is my impression also. It is really too bad that the basis for primacy shifted from doctrinal purity and constancy. Nothing after that early period really is satisfactory but the currently reality is that, on the one hand, we have a Bishop of Rome who rules all of the Roman Catholic Churches around the world, and on the other hand, 15 or so Orthodox Churches lead by a First Among Equals, whose flock is dwarfed by the Patriarch of Moscow. If Canon 34 is applied to relationships between the local churches (a matter of contention between Constantinople and Moscow at this time), then it would seem that it does not matter who is the First Among Equals because unanimity would be required and even the smallest and newest local church can veto anything at any time. So, I do see the logic behind the "First Without Equals" argument that the Metropolitan of Bursa put forth rather forcibly in reply to Moscow's stance. I agree with Moscow's more orthodox position but I also understand that the First Among Equals must more than a chair of a pan-Orthodox meeting. I think that the answer lies somewhere in between. I would think that a start may be to establish a permanent coordinating body that is led predominantly by Moscow and Constantinople, with staffing from most of the local churches. The chair of this body can rotate between Constantinople. Moscow, Antioch, and Alexandria. At the same time, Constantinople would remain First Among Equals with current privileges and responsibilities, while Moscow can be moved to number 2. I know I am dreaming but some out-of-the-box thinking could help us get out of the current impasse.
Also keep in mind that Constantinople being first among equals is small
-t tradition, not big-T tradition. The reason why Constantinople was originally declared such is because, at the time, it was the "New Rome". There were practical reasons why it was granted that status; it was a big, influential city. Now, of course, all that's left of it is in Istanbul, a tiny flock based in a Muslim country.
Nowadays, if they were following the same logic the Fathers used, wouldn't they shift the primacy to Moscow? Of course, doing that canonically would take another unanimous action by a council, and there's no way the EP is going to just give up his right to the title "First Among Equals" in favor of Moscow. I'm not sure what kind of incentives or horse-trading it would take to get the Constantinopolitans to agree to that. Perhaps there's nothing that would convince them, short of a catastrophe (say, if the EP suddenly found itself financially insolvent and had to disband, or if, heaven forbid, the Turks become radicalized and forcibly abolish the EP).