This won't go down well here, but I'll make it clear I love Ronaldo and he's a legend in my eyes. But I'm not completely sold that even if he were to leave Madrid for an Old Trafford return this year, and that's a big IF, that it'd be the best thing in the world for us?!
Can we just put sentiment aside for a moment and look at it logically.
Where does he play?
He's turning 33, he barely dribbles or flies past players anymore, which is understandable. That's a little thing called age. LW isn't probably his most effective position now, Madrid notice this, and have moved him into more central areas last season, particularly in big games. The truth is, Madrid carries Ronaldo as much as his goals carry Madrid, if that makes sense. That's taking nothing away from him or his vital goals, he decides matches even at this age, he's a credit, it's just that he's not the flying machine he once was. But Madrid, with their insane team/squad, can afford to carry him and let him goal-poach as such.
We've just signed Lukaku for a mega fee, who has everything to be the main #9 for years to come, with Rashford, 19, vying with him. Martial can also do a very good job there. That's an average age of 21 between those 3, our CF options theoretically sorted for years, with the likely possibility of Greizmann next season to boot.
I'll be the first to admit if I'm wrong, but Ronaldo to United just won't happen, and probably rightly so. I love you Ron, but I'd prefer to take Bale as he would fit in nicely and has things that Mourinho wants from wingers; pace, good on counters, defensive work rate, with a guaranteed double figure output.