#1 Manchester United

For six seasons, Cristiano Ronaldo vowed Manchester United fans with his sublime skill. From being a raw talent, Alex Ferguson polished him into the brightest diamond of his generation. He helped United win three Premier League titles and one Champions League. Along the way, he also win himself his maiden Balon d'Or. He became a United legend, scoring more than 91 goals in his last 3 seasons with the club.
Undoubtedly, he became the player that he is today at Manchester United. But the split was acrimonious, to say the least. After two years of ongoing saga around his transfer, he finally forced his way to a world record-breaking transfer to Real Madrid. Ferguson wasn't happy with the way he left and United haven't been the same club since then. In fact the last few years have been United's worst in almost a quarter of a century with the likes of Manchester City and Chelsea stealing the top spot.
Ronaldo would feel that he has some unfinished business at the club. If he can lead this team back to the Premier League and Champions League titles he would have made his point of being irreplaceable.
Jose Mourinho is a manager with whom he was worked successfully at the Bernabeu. The Special One has made no secrets about his admiration of CR7. And the two would love to work together again. But can he fit Lukaku and Ronaldo into the same team? A successful move for Ronaldo would also help Mourinho finally banish Sir Alex's ghost from the managerial position at Old Trafford. A win-win situation for both.