It may be time for a return to England.
Now, the obvious first reason that any team would want Ronaldo is simply the fact that he is, by most people's opinions, a top-two player in the world.
With absolutely blistering pace, precise ball control, a deadly eye for goal and vastly underrated heading ability, you couldn't find a team that wouldn't find a spot for the Portuguese international in their squad.
While United don't necessarily need Ronaldo's services—they won this year's EPL title handily without him—he would certainly improve a United wings' corps which features the inconsistent Danny Welbeck and Nani and the oft-inured Ashley Young (per The Sun).
But more importantly, it seems that both parties genuinely want it to happen.
When asked about a potential return to Old Trafford, Ronaldo replied "you never know," proving to United fans the distinct possibility of a reunion.
His love for his old club was also showed by the bittersweet nature of his return to Manchester in their Champions League tie with his current club, Real Madrid. He refused to celebrate after his go-ahead goal and gave the press the following soundbite after the game, per ESPN Football:
"It was unbelievable," he told Sky Sports. "It was an emotional night for me, in both games, but especially tonight. I don't have the words to explain how I feel, but I can use just one word: unbelievable."
With Ronaldo's continual hinting at a return, United have been busy planning a summer coup for their former starlet, with the Daily Star reporting that the Reds are attempting to put together a £55 million deal for him.
However, a move of this financial magnitude may be something the Glazers cannot afford, which is why, according to the Daily Mail, the American-owned club are in talks with Nike for funding that would help them complete a deal of this sort.
United's management most likely never really got over Ronaldo leaving, but his recent remarks have convinced them that signing the star for a second time is realistic and has ultimately sparked Ferguson's interest once again (per Goal.com).
Aside from his well-documented love for the club, Ronaldo's thirst for success may also play a part in bringing him back to his former club. Pending their second leg, Champions League match vs. Borussia Dortmund, (they trail 4-1 on aggregate at the time of publishing) it is very possible that Real Madrid could end this season trophy-less, as Barcelona have regained their place as La Liga's finest club.
United's dominant league performance this year surely won't help Real's case for keeping Ronaldo if they do fail to win silverware.
While United have been involved in transfer rumors circling around Radamel Falcao (The Guardian) and Robert Lewandowski (Daily Mail), it is obvious that, despite being more realistic, these potential transfers would not help United the same way a Ronaldo move would.
Although Ronaldo is probably better than Lewandowski and Falcao to begin with, his experience and success in the EPL should make him the more attractive option for the Reds.
Even with success in Germany and Spain respectively, Lewandowski and Falcao would not be a guarantee to produce in England.
Many players from foreign leagues have had trouble adjusting to the EPL's physical style of play, including first-year United player Shinji Kagawa. The Japanese international has found his form in recent matches, but his slight frame served as a massive disadvantage to him, as he experienced a disappointing stretch that saw him fail to score from September to February and even criticize his own play (ESPN FC).
With a successful season soon to be culminated and what seems to be mutual interest, United would be foolish not to pursue the player who gave them so many fond memories.
(All stats and info via ESPN FC)