The Portugal striker netted his ninth goal of the group stage in a 2-0 win over Copenhagen but the Italian coach was equally pleased with Real Madrid's defensive showing.
Ronaldo's strike in Tuesday's 2-0 win over Copenhagen was his ninth in only five games in the tournament's opening phase, and Ancelotti was delighted for the 28-year-old.
"I do not think [Filippo] Inzaghi is satisfied today with losing his record [for goals in the group stage], but [Cristiano] Ronaldo is a complete forward," the Italian told reporters after the match.
With Madrid progressing as clear winners of the group, Ancelotti pointed to Manchester City as the main side he would rather avoid in the next round, with Manuel Pellegrini's men finishing in second in Group D despite a 3-2 win over Bayern Munich.
"I think Manchester City will be the most dangerous team among those finishing second in their sections. For us, it is important to continue along this path to try to get even better," said Ancelotti.
The former Paris Saint-Germain boss added he was thrilled to see his side keep another clean sheet and paid tribute to the performance of Luka Modric, who opened the scoring in Denmark with a beautifully curled effort.
"The team is close to what I was looking for. Defensively we're doing well. We have only conceded a single goal in our last five matches," he added. "There is a good balance and we have to keep that.
"Modric is doing very well. With Xabi Alonso, he gives the team balance, both offensively and defensively."