#2 Its time for a new challenge

Imagine he returns to Manchester United, this will be a fantastic coup for the Red Devils as he is still capable of scoring 40+ goals this season.
If he can continue that for another 4 years, he could easily surpass Wayne Rooney's 253-goal tally as the club's record goalscorer of all time. He can also break the record for highest number of goals scored in a Premier League season and many such milestones in England.
Or if he joins Paris Saint Germain, he can also break all sorts of records as he will have a supporting team almost as good as the one he has at Madrid. Winning a Champions League and a Ballon d'Or with Les Parisiens will set new records for him, strengthening his claim to be the G.O.A.T.
Also, PSG and Manchester United can easily afford to make him the best-paid player in the world, a wish Real Madrid hasn't granted yet.
Joining any of the Chinese or American clubs seems impossible for Ronaldo at this stage since he feels he still has a lot to offer at the top level of European football.