City captain Dunne, who will lead his side's attempts to keep the Portuguese star quiet on Sunday, rates Ronaldo as one of the world's leading performers despite his reputation for going to ground too easily.
"At times he can be running so fast any nick sends him tumbling. He makes the most of the situation, I suppose," he said. "Some referees give free-kicks but some don't. He is the best player in the world and he plays the game to his advantage. Diving or not diving, he's impossible to mark when he's on form."
Dunne added that so-called 'simulation' was on the increase in what could be seen as a criticism of Chelsea, whose Champions League semi-final against Barcelona was decided by an injury-time away goal at Stamford Bridge in midweek.
"There are a lot more divers these days. It has crept in more and more but you just think 'what goes around comes around'. You dive around and teams score against you in injury-time."