Mbappe has constantly been linked with a move to the Santiago Bernabeu after putting in some scintillating performances for club and country in recent seasons.
Neymar has also popped up on Los Blancos radar in recent years especially after expressing an interest in departing the Parc des Princes last summer, although a return to Barcelona seemed to be his preferred choice.
Mbappe and Neymar have helped PSG reach their first UEFA Champions League final since their takeover by the Qatar Sports Investment in 2011, and they will face German champions Bayern Munich on Sunday to decide who takes home the trophy.
Ronaldo, who won one La Liga title during his time with Real Madrid, has urged his former club to take age into consideration should they decide to move for either of PSG’s superstars.
"Right now, it is not that one is better than another, but if Real Madrid had to make a big investment, they should do so thinking about the future," Ronaldo said during a webinar hosted by Santander.
"Neymar is 28 years old and Mbappe is 22. As an investment, it would be more logical to bring the younger [of the two]."
Mbappe has scored 30 goals in 36 appearances across all competitions for PSG this season.
