I think there is some value, not too much, in those stats - but surely if you use them you can also directly compare Messi and Ronaldo's overall scores?
Messi/Ronaldo, seasons going back from this one to 09/10 (first one available, also Ronald's first at Real)
La Liga:
8.49/7.88
8.68/7.94
8.47/8.06
8.46/7.99
8.84/8.48
8.34/8.27
8.83/8.15
8.88/8.28
8.76/8.35
8.67/8.54
Messi better in every single season.
UCL:
8.72/7.08
8.03/7.94
8.24/8.06
8.28/8.11
8.9/7.83
8.37/8.71
7.75/7.93
8.88/8.43
8.87/7.87
8.44/8.47
Ronaldo 3 Messi 6 (plus this one)
Average rating only tell us part of story on whether the players has been performing consistently better than others over the season, but nothing else. I brought this up because there are arguments that Modric has been consistently among the best player in Real Madrid, which I disagree. And we all know Messi has been more consistent performers over the season than Ronaldo anyway, which doesn't necessarily implies who is better player though.
As I've already mentioned, average rating only serve as part for reference. Apart from average rating, there are also plenty of other criteria we can use to compare players: Stats, Ballon D'or, Trophies, Impact on the winning games/big game impact, and of course opinions.
Since Modric and the other Real Madrid players share the same no. of trophies, we can only use stats, ballon D'or, impact on winning games, big game moment to compare.
In my opinion, Modric isn't top 3 performers for Real Madrid over the past 5 years. But everyone opinions are different, some might think he is top 2 or 3, which is fine.
Average rating, we've already established Modric isn't among the top 3 in Real Madrid. At least it tells us he isn't the most consistent performers in Real over the years.
In terms of stats, surely Modric isn't anywhere near top 3 too, but understandably he is a midfielder, his role is different, so lets just compare him with other midfielders in the same team. From 2014 to 2019, he scored 9 goals and 23 assists in 165 games. Kroos, who played in same team same role same position, from 2014 to 2019, score 13 goals and 45 assists in 167 games. So Kroos is easily better than Modric here. Isco also has better stats, but you could argue he played in slightly more advanced role. But in fact, Casemiro, who players deeper in more defensive role, has better end products than Modric. But end products for midfielder isn't everything, of course. But when compare with players from similar role/position, Modric did score the least points here.
In terms of big game impact, I think we can all agree Ronaldo, Ramos and even Bale are better.
For Ballon D'or recognition, its interesting one. Past 5 years:
Modric finish 1st, 5th, 17th, unranked, unranked
Ronaldo finish 2nd, 1st, 1st, 2nd, 1st
Kroos finish unranked, 17th, 17th, 21st, 9th
Ramos finish 19th, 6th, 20th, unranked, 23th
Bale finish 17th, unranked, 6th, 16th, 12th
So you can say Modric has been top 2-3 in the team in past 3 years, but not even among top 5 in those years prior to it. Over the years, whether he is top 3 in the team, remained debatable.
