You are judging on one game by Lukaku. Quadrilateral and Immobile were top scorers in serie A in Ronaldos first 2 seasons. Both of them are really mediocre. And Lukaku had more assists (send most in serie A).
I'm not saying Ronaldo won't score; after all City creat more chances than anyone but to say that he was a success in Juve is a monumental lie. He played for the most dominant team in serie A which has unfortunately become rubbish.
Over past 3 seasons in Italy, no one come close to Ronaldo in matching his goal tally:
1. Ronaldo - 101 goals in 131 games
2. Immobile - 83 goals in 137 games
3. Quagluarella - 51 goals in 101 games
Over past 2 seasons, similar:
1. Ronaldo - 73 goals in 90 games
2. Immobile - 64 goals in 85 games
3. Lukaku - 64 goals in 95 games
He is also top goalscorer in Euro this summer.
Yes it’s only 1 game for Lukaku, but one could already tell he is going to be huge and will score a lot in Chelsea.