Benzema has found it tough to establish himself at Madrid with Gonzalo Higuain often preferred in the lone striking role, while Ronaldo, who played his final farewell game in Brazil's friendly 1-0 win over Romania on Tuesday, bowed out of the game on Wednesday after a glittering career that included three World Player of the Year awards and two World Cup wins.
Yet, despite all accolades collected by the Brazilian in his playing life, Dudek - who recently announced his own decision to retire from football - thinks Real Madrid currently have a better player.
"When I first saw his [Benzema's] first training session, I was impressed," Dudek said in an interview with France Football. "I told all my friends that Madrid had signed an extraordinary player. For me, he is even better than Ronaldo, the Brazilian. Karim has incredible qualities; he is fast and he is elusive, and he has an eye for goal."
Asked if Jose Mourinho's preference for Higuain has stalled Benzema's progress, the Polish goalkeeper said: "Mourinho has a very strong personality but he is also a psychologist.
"He never leaves a player to the side. He knows how to psychologically motivate a player if he believes he can bring something to the group. This first season in Madrid has been difficult for him, but he works for the future of Real."