Charlton admits he's a huge fan of the Portuguese.
"I was really sick when Ronaldo left us," he told the Daily Mail. "He wanted to be the biggest player in the world and didn't think he would get that from Manchester United. He would have, though.
"He is scoring goals like I have never seen. He is just sensational. He shoots, he heads, he scores. He does all the things that anybody who loves football would like to see. He's magic. Who knows, maybe we would one day have the opportunity to get him back here.
"We played one game at Chelsea and he scored from 40 yards. The goalkeeper saw the ball from off his foot but it moved about three or four ways and the goalkeeper just couldn't get in position.
"The first thing in his mind when he gets the ball is, 'Can I score?' He doesn't think, 'Can I pass it to somebody else?'
"Maybe he would have frustrated me if I had played with him but as long as you are winning you can't criticise him, can you?
"When we win at Old Trafford, Alex encourages the directors to go into the dressing room and speak to the players. I sometimes used to go in at that time but there wasn't much I could tell Ronaldo. I just used to say, 'Well done'."