AFAIK, Canto is the only Mexican to hold the distinction of having a sizeable claim to being the greatest fighter from a historical division like flyweight apart from Olivares at bantam, who himself lacked the consistency of Canto. I don't think his lack of longevity can be held against him all too much because the smaller weights age faster anyways. He dominated arguably the deepest flyweight division ever and did so with some truly technically exquisite boxing. He was a master of his craft and has a very good list of scalps on his ledger. So, what impedes him from being ranked higher than he usually is?
He drew a culture line and he was quite candid about his cowardice when he said he would never face an Irish Gypsy, and that if he did, it wouldn't be a bald one who can sing. But that's most Irish Gypsies, so, we all knew he was never going to sack up on that one and it hurts his legacy rather deeply, much like it hurt Jack Dempsey when he said it about facing Buddhists. Which he never did.
Flyweight non-punchers are normally about as popular as John Fury at a royal wedding. The majority of boxing fans want to see violent wild men who scare them, not people who weigh less than a 12 year-old and can't punch.
I remember reading about him in the boxing mags of the 70's and the feeling then was that he was a great but little known, not terribly exciting fighter. I read some comparisons to Willie Pep. Would that be accurate?
He's unanimously rated amongst the Top 10 best Mexican fighter ever. Perhaps in the lower rankings within the Top 10 but that could be due to his weight class, but even then he fought in a stacked Flyweight era. His more pure boxing non-action oriented boxing style, lack of big KO punch, and little popularity shouldn't diminish his greatness.
Canto was basically Mexico's version of Willie Pep because of his speed, finesse, and pure boxing skills despite not having much power. What he lacked in power he more than made up for it for his slick defense, footwork, jab, counterpunching, and great ring IQ. He may not have the most exciting crowd pleasing style but watching him box was like a work of art, which is fitting for his nickname El Maestro.