He's better than Ronaldinho for me either way. Ronaldinho wouldn't have 2 Ballon D'Ors playing at the same time as Messi/CR7.
Far better longevity at the top and he's been better for Brazil than Ronaldinho has.
If he has a great WC, I think Neymar would edge it clearly for a wider spectrum of people.
It's a difficult comparison. If the argument is Messi, Neymar and Cristiano scored more, then that is true. But Ronaldinho hit his peak when the game was more defensive - as the success of Greece, Porto, Benitez's Liverpool and Mourinho's Chelsea showed - and less imbalanced between the elite clubs and the rest. Barcelona scored 60-80 goals in La Liga every year from 1999 to 2008. And then in the decade that followed they averaged 95-116 goals a season, around 50% more. And the numbers of the attackers benefited accordingly.
And fundamentally he was a different type of player - much more a creator and much less a goalscorer. For every goal he scored, he provided 0.8 assists. Most modern wide forwards at top clubs provide just over half that. To give a few examples:
Ronaldinho 0.82 assists per goal scored
Neymar 0.62
Mbappe 0.51
Salah 0.50
Messi 0.47
Cristiano 0.32
If the argument is he didn't win as many games as Cristiano/Messi did, then that is true as well. In his defence I would say it's very hard to quantify how he unlocked space through his unparalleled close control and creativity. It's not unlike how Zidane's mastery of the ball - which drew defenders to him like a magnet - cannot be reduced to just goals and assists. Neymar and Messi had a lot of that too, but I think the difference is their teams more frequently enabled them to use that skill closer to goal.
Both Ronaldinho and Neymar remain great "what if"s to me. Ronaldinho because he failed to crown his status as the best player in the world at the 2006 World Cup and didn't a sustain a lengthy career at the top that would have added another layer to his legacy. And Neymar because he has been consistently brilliant in the build-up to the most decisive moments in his career and then hasn't quite been able to see that through, either through injury or his own in-game decision-making.