The Greek verb here "gennetois" is masculine, which is why, for example, the NEB translates this verse as "Never has there appeared on earth a mother's son greater than John the Baptist". It is also the case that Jesus is referring here to the the prophets of the old dispensation, among whom John was both the last and the greatest.
-A8
I have seen posted on this thread that the proof that Mary was without sin is that: "We know that Mary was sinless because the angel Gabriel declared her so ("full of grace")."
How do you know that Mary was "full of grace" continually throughout the rest of her life? Or, was this true at this instant (and other points in time) in Mary's life? In the O.T. we see many examples of men where we are told that they had the Spirit of God and then at a later point the Spirit of God had departed from them. As a matter of fact, I believe that it would be consistent with Catholic belief to say that an individual is ultimately close to God at singular points in time, and then sins, so that only through Confession can they once again be close to God.