What really made this rivalry catch fire was their incredible, unprecedented goalscoring rates, with both Messi and Ronaldo averaging more than one goal every game at their peaks.
During the 9 years Ronaldo spent at Real Madrid, Messi and Ronaldo both scored a goal every 85 minutes in all competitions. The adjacency of their goalscoring—matching each other blow for blow—has been astounding over the years.
Over their entire careers, it's Messi who edges the ratio, with 0.79 goals per game, whereas Ronaldo has scored 0.73 goals per game. If we drill down into goals per minutes, Messi scores a goal every 104 minutes, and Ronaldo scores a goal every 111 minutes.
Ronaldo still has more all-time career goals than Messi though (Ronaldo has 976 career goals and Messi has 919 career goals), but Ronaldo has played 166 more games over his career than Messi has.
Although Messi shades the overall ratio, Ronaldo spent more of his formative years as a more traditional right winger, only really starting to focus on goalscoring as his primary function in 2006, 3–4 years into his career. For Messi, it was 2–3 years until he completed the transformation from a nippy winger into a player hungry for goals above everything else.
If we take these differing beginnings into account, the ratios would be even closer. Of all the categories, goalscoring is the hardest to separate them on.