"Yes, undoubtedly Ronaldo is number one," the 55-year-old Italian, told a news conference at the Vasil Levski national stadium in Sofia on Tuesday. "I don't want to offend other players I've coached, but he's my number one."
Ronaldo, last season's Champions League top scorer with 17 goals, has been scoring for fun in recent weeks, with eight in his last three matches, as Real netted 15 times against Deportivo La Coruna, Elche and Villarreal in La Liga.
When he struck in Saturday's 2-0 win at Villarreal, the Portugal forward became the first Real player to score 10 goals in the opening six games of the league season, breaking the record set by club greats Alfredo Di Stefano and Amancio Amaro.
"Cristiano is an outstanding professional," added Ancelotti. "He's committed to the team and the club, he doesn't talk much, but he is a leader.
"He scores more goals under a coach who puts him in the right scheme."
Real thrashed Swiss champions Basel 5-1 in their Group B opener but Ancelotti has warned his team not to lose focus against Ludogorets, who are making their eagerly awaited group-stage home debut.
"Ludogorets play a very dynamic football. They're pushing their opponents, so we realise what team we'll play against," said Ancelotti.
Tenacious Bulgarians
The Bulgarians were tipped to struggle in their first appearance in the Champions League group phase.
However, the Razgrad-based side have been impressive with their tenacity and ball skills, finally losing 2-1 to Liverpool only after a penalty in added time in a pulsating match at Anfield two weeks ago.