I have met people who credit Gerry with their entry into the Church. I have met far more who have credited Steve Ray or Al Kresta or Jeff Cavins. I have met even more who have credited Scott Hahn. Other names could be added: Fr. John Corapi, Fr. Benedict Groeschel, Peter Kreeft, Jimmy Akin, and more, both clergy and lay.
The problem is that most of the people influenced by the above named apologists, theologians or clergy have to have their theology cleaned up. That's where Gerry generally comes in. One of the reasons Gerry is so successful in his ability to move people with the Catholic truth is that he jettisoned his Protestant errors while someone like Hahn can't resist relying on his "old professor of Bible" etc. Just ask Groeschel or Fr. Pacwa about EENS. They are in obstinate denial of a dogma of the Church. They make Catholicism absolutely meaningless for salvation. They are effectively no longer Catholic in their hearts if read by their stated beliefs.
If people are coming into the Church however haphazardly by way of the Half-Cath/Half Protestant convert apologists. They come to understand "the fullness of the faith" by way of Gerry Matatics.
Well, if you say that only converts who believe as Gerry believes are real converts, then by definition Gerry must be the most successful convert maker. But if you allow a wider definition of what constitutes a Catholic (perhaps the test might be: Would Benedict XVI consider this person to be a convert to the faith?), then Gerry can't be considered anywhere near the top of the list. The numbers just aren't there.
Do you believe Baptism of Desire is salvific, as defined at the Council of Trent? It doesn't appear so. Wouldn't that make you a heretic in obstinate denial of clearly stated truth?