For the majority of the Christian era, the overwhelming majority of Christians were either Roman or Byzantine Catholic. That is simply a matter of history, despite how it might rub your anti-Catholicism the wrong way.
The only Christian populations that I can think of that existed for long enough in high enough numbers to even creep into that Catholic majority are the Armenians and the Copts. And while they existed for long enough, they never existed in sufficient numbers to challenge the Catholic majority.
For the majority of the Christian era, the majority of Christians were either Roman or Byzantine Catholics.
Still holding out hope for Prester John, or do you not even know who he was supposed to be?
I don’t know who Prester John is supposed to be.
How do you define Christian? A bunch of people on some guys roles who partakes in mass now and then and helps an old lady across the street does not a Christian make.
You can't say that with certainty because you don't know if any individual is a Christian or not.
The overwhelming majority of Catholics are Catholic, nothing more and nothing less.
You can't define them as Christian by virtue of the fact that they're Catholic because denominations do not Christians make.
One is a Christian based on their relationship with Christ, not church affiliation or membership. Therefore you cannot say that most Christians are Catholics.