It is believed that Ronaldo started his career with Manchester United. Manchester United bought Ronaldo from Sporting CP for 19 million. Ronaldo performed brilliantly in the 2007-08 season. And in this season, Manchester United won two titles, the Premier League and the Champions League. Manchester United was able to win these two titles because of Ronaldo.
He was grown up to super star level in Manchester United but after one successful season with them, he wanted to leave and join Real Madrid. Sir Alex Ferguson tried a lot to convince him to stay with the club one more season, but it shows that Ronaldo does not have things like strong bond with Manchester United. He is ambitious and what he looks for are titles, awards and more.
Saying all titles won in these years are because of Cristiano Ronaldo is not accurate. He is their brightest star player but we saw that he got a lot of support from Rooney, Tevez, Berbatov and other players. We saw that after Cristiano Ronaldo left Manchester United, Rooney scored more goals and the same with Real Madrid and Benzema. He would have not achieved these seasons and titles without considerable sacrifice and support from his teammates in Manchester United and Real Madrid.