I was watching this video of the Japanese-YouTuber Hikakin beatboxing the first English Pokemon song. It made me wonder: was the English dub theme song more well-known than the original Japanese opening?
The following answer is based on the results I got on Google [from my country (France)].
Keeping the following elements in mind, one can say that their popularity level is more or less the same.
In red : the English, in blue : the Japanese
Except for the year 2005, the search trends looks to be pretty similar.
Surprisingly enough, the countries which searched the English opening on google were the following ones :
For the Japanese opening, the searches come only from Japan.
The most viewed youtube video of the Japanese opening (in my country) views ~1 million views.
The most viewed youtube video of the English opening (in my country) views ~1 million views
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.