Well, he's a poacher like no one else out there, he knows to to score from very little he gets. Other than that he drags them with his sheer willingness and competitiveness. That stuff can get you only so far, he's not the same player anymore. United are suffering from the same disease Juve did: everyone plays for Ronaldo, nobody takes responsibility anymore. For sure many of their fans think otherwise but luckily it's not our problem.
In Portugal he'd score shitload of goals, in EPL they're on a downward spiral.