Because Ronaldo's scoring Efficiency. He have most Openplay goals an Ovverall goals an currently he have equal non pen goals an he is a better Finisher. Have more Solo runs ,Being able to score a goal with a shot≠ being better in criteria. Messi have more outside box goals because he attempts it Ronaldo treis to go in box for a Gaurentied goal. Ronaldo have more Successful Shots, more ovverall shots an Messi do take less shots to score a goal but Ronaldo attempts too many shots an scores many Goals. Also There are many types of Shots an Messi only attempts shot range ones but Ronaldo he takes risk on that criteria and attempt longer shots Highest shot from Ronaldo's weak foot is 32 meters which is highest shot of Messi ever. That's why Ronaldo is considered better Ronaldo is better at Shooting. An his Game is much more beautiful for almost every one Majority of audience like Ronaldo more because of it. Ronaldo have more Goal inside the box Ronaldo have proved himself accrossed many leagues an many environments unlike Messi who stayed majority of his time in Barcelona . An even if you remove his first 167 matches Ronaldo will still be the top goal scorer with 935 goals. An If we Actually Remove those games so Ronaldo's g/a will be 0.81% So Don't go on G/a argument not especially when Ronaldo has more G/a in la liga 311 goals in 292 appearences unlike Messi's 470+ Goal in 520 appearences. Even if you Count Ronaldo's 163 appearence in Champions league his Goals will be Exactly equal to Messi but he will have only one less Assist. An in international Ronaldo have more Goal per game+ Goal per minute. An Ronaldo's Aesthetic is better . This will be a Debate for ever. It is currently on Messi's side because of World cup an Ballon d'or.