In North America the English Theme is more popular, but in Japan the Japanese one is. This is because Japanese people hear the Japanese theme on tv and Americans hear the English one. In Germany the German version of Gotta Catch Em All is most likely more popular. Further more, people prefer the one they can understand. For english speakers it is Gotta Catch Em All. For Japanese speakers it is Mezase Pokemon Master or Aim to be a pokemon master. English is more widespread so more people will prefer the English one. I am a native english speaker and prefee the japanese theme. This is because I got sick of the English one.