Ronaldo is not going anywhere for the time being. I think all he cares about is the money. Why else would he stay at United when he knew he wouldn't be a starting player again? He had the choice of clubs. United are not playing the Champions League this year, there were plenty of clubs he could go to and play CL. Shame to see a great player fade away. I think PSG has made quite an impression so far. In my eyes they are the favorites to win the title and not City.
Thinking about Ronaldo feels very bad. Ronaldo will never be like Messi. Messi has some unique talent that allows him to adapt everywhere. But Ronaldo does not have that ability. Ronaldo's form is losing to age day by day. He lost his ability to play 90 minutes. I don't know if he will return to form. Good luck to him.