The evidence is in his pace physique touch & ability he has already showed to strike a ball.
Whether he can raise that to the level of Ronaldo is another thing, but the raw ability is so obvious even Gary Neville has noticed it.
But as I just posted, he works twice as hard for the team as Ronaldo ever did, so if he reaches anything like the same level in other areas, he will automatically become a similar calibre of player.
He has most definitely not had it easy at City & works much harder without the ball over 90 mins as Dennis Tueart for example, who was never considered a 'lazy' player.
And if he is expected to work even harder, it is unlikely he will ever be quite as good as Roaldo in the other aspects. It's close to impossible to do both without one area suffering.
And yes btw, we have had a load of players at City in recent years with more talent than most I've seen at City & elsewhere, in the previous 50 & none have yet made it at any level, which I'm not pleased about.