I think you guys are getting it all wrong the Elclasico has always been big even before Cristiano Ronaldo and Leonel Messi both reached their prime. The Elclasico has always been an important fixture in the Spanish La liga season. This is bigger than the player, it's a rivalry that would always be big any day any time. Yes Ronaldo and Messi gave it more appeal from neutral fans (non real Madrid or Barcelona fan) but anyone who is a core fan of both team or a strong follower of football would always anticipate this fixture.
El Clasico is very crucial match despite without Lionel Messi and Cristiano Ronaldo, I blame with many people still said not interested with El Clasico match after Lionel Messi and Cristiano Ronaldo departure from La Liga competition. Before both players are popular, el clasico have been interested and there are not problem have Messi and Ronaldo keep make more attention with El Clasico match. Its great rival between Barcelona and Real Madrid in La Liga always more interested with el Clasico match despite there are not Lionel Messi with Barcelona and Cristiano Ronaldo for Real Madrid, exactly Madrid have leaves by Ronaldo last several years and they got many tittles and seems there are not really important when have one player leave club because still have other player will replace his position.