The Italian coach has nothing but respect for both players but he feels that the Barcelona man has a slight edge over the Portugal international.
Ronaldo beat Messi to the 2013 Ballon d'Or earlier this week but Capello feels that the Barcelona ace still has a very slight edge on the Real Madrid superstar.
"These two are two phenomenon," the Italian told MARCA. "They are different, though. Cristiano is a great player; so strong physically, so powerful. Messi has more creativity.
"Having either of these two players on your team is a guarantee that at any time you can change the game."
Messi's Barcelona currently leads the Primera Division on goal difference from surprise package Atletico, with Madrid just three points back in third.
However, Capello is backing Los Blancos to end the season on top of the pile.
"I see Madrid as favorites to win the league," the former AC Milan boss revealed. "But we will see. The change of coach at Barcelona [Gerardo Martino for Tito Vilanova] has brought different things to the team. They play a little faster now. They are still as offensive and score a lot of goals, but I think the team is still adjusting to the coach.
"It will be an intense fight and will not be decided until the end, but I think Real Madrid will win. Analyzing it, I think Madrid and Barca are more likely to go all the way in the title race but seeing the spirit that Atletico has makes me think they could fight right until the end too."
Meanwhile, Capello believes it imperative that FIFA decides against staging the 2022 World Cup in Qatar during the summer.
"You have to play in winter," he declared. "Given the temperatures in the summer, there is no choice.
"Mainly for players but also for fans who will travel there, so that they can enjoy the tournament more."