...is in the eye of the beholder, so saith the old saying. And apparently it's in the ears too. Yes, what constitutes "good" or "pleasing" for one person may not necessarily be similar to what it would be for someone else. (Traditional Chinese Opera is an excellent example of this, especially for the modern Western audience.)
And yet, I always cringe whenever I hear someone say something like "Japanese is a beautiful language!" Especially when it's in the context of "despite the fact that this movie is American, I want to watch it in Japanese because ..."
Somehow, I doubt the rabidly obsessed are either objective or educated to actually make such an assessment. Sure, in the West, we tend to say the same thing of the Latinate languages -- of Spanish and French, and conversely we tend to think of German and Russian as being "harsh" and "masculine", perpetuating such jokes that imply that German terms of intimacy still sound like swearing to the rest of Europe.
Pure rubbish. True, there are differences in the phonetic ranges of these languages, some of which may lie well outside one's own native tongue. For English or Cantonese speakers, for example, Mandarin may sound more pleasing because of its lack of glottal stops. Somehow, glottal stops are considered masculine or ugly. Or the regularity of (the five) vowel sounds (and three diphthongs) in Japanese might be refreshing for any speaker of the PIE language family.
But if an individual is a "young adult" male, reclusive and obsessive about Japanese animation, is it more likely that this person is actually finding Japanese to be a beautiful language, or is it more likely that in a case of self-induced hypnotism (or delusion), he's convinced himself that Japanese sounds so much better.
In fact, from personal experience, I've found that not only do such individuals who worship Japanese have minimal linguistic understanding (despite their obsession compelling them to learn the language), they have an even weaker understanding of their own native tongue (which in my case, would have been native English speakers). "Japanese is so much better than English; it's so much richer in vocabulary". Yes, well, maybe if you'd bother to read Chaucer,or Puttenham, or Shakespeare, or James Joyce. Or perhaps the poesy of Edgar Allan Poe and Rainer Maria Rilke. But no, clearly your extremely limited exposure to your native tongue is obviously enough to compare to the best of the literature of another language.
On the other hand, I sometimes wonder if it's even worth the effort to try to show this obvious fallacy in these rabid fans' philosophy. If I'm getting paid to teach, I shouldn't care what they do with the material taught, right?