This is not up to debate. Ronaldo, and it's not even close. Garduiola Barca team was called the best in the history, yet they couldn't even win 2 CL in a row, and their both CL was due to heavy referee help, especially that against Chelsea, which was the biggest robbery in the football to date.
But still with this blatant cheating, Messi has 3 CL where he was the figure, he actually have 4, but he was a reserve and i don't see a reason to count it.
Ronaldo have 5 CL, 4 in RM in 5 years time, and they won CL 3 straight time, and no one was even close to do it twice, forget about doing it three times. Especially in RM he was the main reason for this CL, and even with us.
The numbers speaks for itself: 8, 17, 16, 12, 15 is the goals he scored.
Should we even say that Real name was, Round of 16, before Ronaldo moved to them and transformed them ? And they are also doing a great job after he leave as well.
And European Championship > Copa, as Copa is a joke of tournament.
Since 2004, there was obviously 5 European Championship, while there is 7 Copa. Just look at this numbers, 2015 Copa, 2016 Copa, 2019 Copa, 2021 Copa, what is this joke ? Not to mention the quality of the teams is like 10x lower, and that you have like 1-2 hard matches before the Final. There is no such things as qualifications, and from a groups of 5, 4 team is moving forward, like really ? And on top of that, you have exactly 3 more matches to win.
Prime for prime, the only thing Messi had over Ronaldo was his dribble, and that's it. Ronaldo was obviously a better header player, more stronger physically, faster on both accelerating and top speed, better with the weak foot(if we call them equal with the strong one), best positioning in probably the whole history, a true leader and way more clutch, and he was also an absolutely monster 1 on 1, as people looking him currently loves to forget that. But they both were great in beating players 1on1.