Edgardo Bauza's Argentina are struggling in World Cup qualifying, sitting fifth in the table with Messi having featured in just five of their 12 matches.
Riquelme, who made 51 appearances for his nation, said Messi's absence reduced Argentina to being just like any other team.
And he feels the same happens to Madrid, who are top of LaLiga, without four-time Ballon d'Or winner Ronaldo.
"Argentina without Messi is a normal team, but this of course the best player in the world," Riquelme, who won 51 caps for Argentina, told Canal 13.
"The same thing would happen to Real Madrid without Cristiano Ronaldo."
Ronaldo has scored 19 league goals, four fewer than Messi, to help Madrid top the table ahead of Barcelona.