"Ronaldo is amazing," said Fabregas, whose table-topping Arsenal side are two points ahead of United.
"I admire his physical body, his power, he is so quick with the ball and he has such strength.
"He is a player that at any moment can score a goal for the team and make the team win - even if it is a header, left or right foot.
"For me, he is an exceptional player."
He added: "It is good that people say they enjoy watching Arsenal, but when I watch teams like Manchester United, I really enjoy watching it myself."