When I was growing up, some of the most intense sports rivalries were the Detroit Red Wings/Colorado Avalanche (Hockey) and the Miami Heat/New York Knicks (Basketball). Those died out as players changed teams over the years. You can also throw in the Red Sox/Yankees rivalry, but it has lost its steam a little with the Yankees missing the playoffs twice in 6 six seasons. So as I had the opportunity to live overseas, I was only exposed to soccer. ESPN became a distant memory and had to adapt to ESPN Deportes.
As I honed in on soccer, there were two teams that were exclusively displayed on TV: Barcelona and Real Madrid. After all, they are most successful clubs in all of World; They just happen to be Spanish. This means they have clashed in league competition, Copa del Rey, and in the Champions League. In fact, Real Madrid has won 90 matches; Barcelona has won 86.
This rivalry goes deeper than soccer. F.C. Barcelona, which plays in the capital of Catalonia, has always represented Catalan pride. Catalans have always opposed the centralized views of Madrid dating back to the 1930s. In fact, Catalans have pushed to separate from Spain and become an independent state previously. Madridistas, those that reside in Madrid, aren't too fond of the Barcelonans either. In fact, they are not pleased with Barcelonans speaking Catalan, as opposed to Castellano, which is widely-spoken through Spain.
The rivalry also extends off the field. One of the greatest Real Madrid players, Alfredo Di Stefano, was once pursued by Barcelona. The Catalan club gave up on the pursuit. Some players like Portuguese, Luis Figo, have caused controversies by playing for both clubs at one point in their careers.
There have been many memorable sports rivalries that included brawls, battles for a title, pursuit of free agents, and team executives publicly taking the fight to the airwaves. Unlike American sports rivalries, this rivalry between Barcelona and Real Madrid has never lost its intensity. There have been an infinite number of coaches, players, and presidents replaced and the new guys to the rivalry just pick up where their predecessors left off. On an international level, there's nothing like this.
I'll be watching this game comfortably and know that I won't be disappointed. This rivalry never does.