I did never heard an opera sung in a language that is not the original, but heard many popular songs translated. The outcome is a completely different thing. Each word, each vowel and each consonant has a place in the flow of the melody, and once the music is joined with the lyrics and the action, there's nothing that could express the same in another language.

Curiously, one of the most important patriotic songs in Argentina, is named Aurora (Dawn) and sung in Spanish as an homage to the national flag. But the song was composed in Italy by an Argentinean composer, Panizza, in 1912 as an aria of his purely Italian opera Aurora, which was not "dawn", but it was the name of the female main character (like Aida, Carmen, Tosca..) This deeply beautiful aria has been sung by children for almost one century, and none of them has really understood the mess of Spanish words put there together by two respected poets some years after the opera was composed. Since it would be outrageous to sing it in Italian, there is now a controversy about changing the lyrics again, because it did never make sense !

I agree that the translated subtitles are acceptable, but I would prefer those subtitles showing us the original lyrics.

Un abrazo,
Andrés