The former Real Madrid manager believes the 31-year-old, whom he won the Champions League with two and a half years ago, still has a lot left in the tank
Ronaldo was crowned Ballon d'Or winner for the fourth time on Monday after helping Madrid and Portugal to Champions League and Euro 2016 glory respectively in the last 12 months.
Zlatan no Messi or Ronaldo - Shearer
The 31-year-old scored 51 goals in all competitions for Madrid last season, while he netted three at the European Championship in France, but despite his exploits, there is a belief that Ronaldo's best football could be behind him.
However, Ancelotti - who teamed up with Ronaldo to win the 2014 Champions League with the Spanish capital club - believes the Portugal captain has plenty left in the tank, having seen him score 10 LaLiga goals already this term.
"I don't know when he'll keep going until, but I don't think he's that old," Bayern Munich boss Ancelotti told AS.
"Playing in a more advanced position could have an influence. He's now playing more centrally and with time he'll have to drop deep less often and stay in a more advanced position.
"I think he'll keep up this high level for three or four years."
The ex-Manchester United star is now just one Ballon d'Or short of Messi's all-time record and the Italian thinks he doesn't get enough credit sometimes for his impact on the sport.
"I think it's deserved, because Ronaldo won the Champions League and the European Championships," Ancelotti said. "He's performed better than the rest this year and the award is a logical one.
CARTOON: Messi's getting married!
"For many this is the era of Messi, but it's also the era of Cristiano. The competition between them has improved them. Messi is better because he's had Cristiano, and Cristiano is better because he's had Messi.
"Without doubt he can [add to his collection] over the next two or three years. Like Messi. The rest will still have to wait, although we can help some of them as a team, such as [Robert] Lewandowski for example, if we win lots of trophies."