Yeah I came to make the same comment. But Messi and Ronaldo didnt play each other that many times in the grand scheme of their careers. A big part of the comparison is statistical. Trophies, records and so on. Tennis might be a better comparison because to win a grand slam, Sampras really had to beat Agassi.
I don’t disagree with your general point, but Messi and Ronaldo absolutely have played directly against each other a decent number of times — a quick google suggests 30 head-to-heads in the “clasico”, supposed to be one of football’s biggest rivalries.