World Player of the Year Messi was compared to Real great Di Stefano by Atletico Madrid coach Quique Sanchez Flores on Saturday after the Argentina forward netted his fourth hat-trick of the season in a 3-0 win over Atletico.
Ronaldo, the world's most expensive player, scored twice in Real's 4-1 home win over Real Sociedad on Sunday and Valdano, a former Real and Argentina forward, said the Portuguese was the Di Stefano of the 21st century.
"It is not Messi, it is Cristiano Ronaldo, who what is more wears the same shirt," Valdano said in a television interview.
"He is a very important player who is set to make history at this club," he added.
"We wouldn't swap Cristiano for anyone, although one must recognise that both he and Messi are two very high-quality players whom it is a privilege to have in La Liga."
Barca set a new record for consecutive league wins of 16 on Saturday, eclipsing the mark reached in the 1960/61 season by the Real team that included Di Stefano, considered one of the greatest players of all time.
Now 84, he helped them win the first five European Cups between 1956 and 1960, scoring 418 goals in 510 matches, and later became the club's coach.
Ronaldo's double against Sociedad drew him level with Messi on a phenomenal 24 goals at the top of the La Liga scoring charts with 22 matches of the season played.
The pair are set to renew their rivalry on the international stage on Wednesday when Portugal play Argentina in a friendly in Switzerland.
