Japanese, when sung, sounds amazing to me. I’m not sure why exactly, I just love the sounds; mostly CV syllables of course. But when it’s spoken, it’s not my favorite—it’s spoken too quickly and many sounds are eliminated (silent vowels and such).
Latin also sounds excellent, not that I really hear it being spoken. But I think it can be beautiful and a far cry from most people’s image of it as the creepy language used to summon evil forces.
As a linguist, I look at languages all over the world and I have a collection of songs that I have for no reason other than to hear the sound of the language; thus I don’t really find any language to be “ugly-sounding”, though I can understand why people choose certain ones. English-speakers tend to love the sound of Latin-based languages: French, Spanish, Italian, and tend to dislike languages with high amounts of consonant clusters and velar fricatives like German and Russian. I’ve also heard Vietnamese called “ugly”, probably for its unusual vowel sounds.