He admits that there is little to choose between Ronaldo and reigning European and World Player of the Messi, but feels Real's Portuguese goal machine just gets the nod.
"Messi is extraordinary," Kaka told Brazilian television.
"To say who is the best player in the world is relative because a lot depends on what you do for the collective.
"He and Cristiano are the best in the world, but in today's game, in the modern game, Cristiano is the most complete player in the world.
"Cristiano can score goals with his left, with his right, with his head and from set-pieces. Messi is excellent with all the great things he has, but Cristiano is a more complete player than him."