Which language sounds most beautiful?

Anglo-Saxon or Icelandic, maybe. Some old languages, like Gothic or Latin may do.

Persian

I really like the way Korean sounds.

Japanese is hands down my favorite language to hear

I think the language depends on the person speaking. I have one friend in Germany who I think has a voice of the German gods, but other German speakers pale in comparison. Then theres another guy who speaks radio quality Russian, and someone else with a cute canadian accent.

English is my favorite. It's soft and sounds good in music, poetry, etc.

Italian to me, but then as OP says, I’m biased because it was my first language.

Vietnamese or Cantonese

Other, namely Gaelic.

Russian sounds beautiful imo.

( And maybe the likes of French, Chinese, Italian, Polish and many others )

Okay, i'm gonna go with Estonian on this one :)

Spanish

Welsh. They have an alveolar fricative.

Navajo also has an alveolar fricative, but it's also a tonal language so it loses points

Volapük binon pük jönikün.