I'll only say Real Madrid &Barcelona fans, since they're the two biggest clubs in the world and I support Barcelona and have been to one of the El Clásico games, so I know what it's like to be one of the loudest and most passionate ones.
True Real and Barca fans are great however like most other big clubs ex: Man U, Arsenal there's definitely a lack of atmosphere for smaller less important games. This is simply because after getting a taste of European nights especially Semis and Finals, cup finals etc. playing a team with a starting lineup of 20m pounds in a city with 20,000 people suddenly becomes quite anti-climactic. Teams like Atletico and Valencia will continually out-sing and out-chant the bigger teams even when playing less important games because it's all they get.
