Ronaldo was at his brilliant best once again as Real eased to a comprehensive La Liga win on Saturday, the Portuguese scoring one goal and setting up two more.
His performance continued a stunning start to the campaign that has already yielded him a personal haul of 22 goals in all competitions.
And Ancelotti is running out of superlatives for the reigning Ballon d'Or holder.
He said: "Talking about Cristiano is something that is becoming a hard thing to do; he's simply fantastic."
Crucial to Real's win was scoring early, with Ronaldo's second-minute strike preceding a double from James Rodriguez - which came either side of a goal from Karim Benzema.
The result backed up last week's El Clasico success and Ancelotti was understandably delighted with how his men are playing.
He added: "The first goal opened the game and we had the opportunity to play with more space.
"Of course we have faults but I'm pleased with how we're playing. Everything is going well and hopefully it stays that way."