Last season Ronaldo was, well, incredible as we all saw. His 42 goals and general play was a massive part of us winning the League and Champions League. However, this season isn't going particularly well for him. We wouldn't have been as successful without him last season, even if we had Messi.
Talking about the topic question. Well, I'm getting a bit fed up with Ronaldo and, although I think Ronaldo has more to his game atm, I think Messi will become a better player than Ronaldo.
Would I swap them? Well, I know many will be surprised but I would say no. Why? Well, because I just don't know if Messi would be suited to the Premier League. He would be a star for us in the Champions League no doubt, but it wouldn't be worth the swap if he wasn't to be suited to the Premier League.
If we were discussing swapping Ronaldo for Ribery, I would have no hesitation, especially if we were to buy a striker along with it. As I said in the summer, if Ronaldo was to leave I think we'd need to replace him with a winger and a striker.