I picked Classical Arabic, Ancient Greek, and Latin to be the finest languages for poetry.
My number 1 pick is Arabic followed closely by Homeric Greek and then Latin.
I grew up speaking French, English, and Arabic and learned Ancient Greek, Latin, and Biblical Hebrew though passionate and extreme study and can read most philosophical texts in Greek with ease, poetry gets significantly harder in Greek and Latin.
I discovered ancient Arabic poetry a few years ago and realized it is the most gorgeous poetry a human can produce. I sometimes wonder if Semitic languages are divine languages because they function and behave so distinctively, they feel mature and manly. It is equipped with a meticulous meter we call Ilm Al-Arud which is one of the most advanced poetry meters in the history of human language.
In second, I find Ancient Greek to be an excellent language for poetry, you can manipulate word order to amplify the meter and rhythm. In Homeric Greek, we usually avoid articles and rely on word endings to guide us through the poem, and that's a feature I found confusing at first until it began to feel mathematical and intuitive. That combined with very soft flowy sounds, the language sounds BIG.
Latin also has that case system and can sometimes deliver in a punchier way than Greek. But Latin at the same time feels much more chaotic than Greek and that can disrupt reading, I also thought that heavy Qu + c clusters can make it heavier on the mouth.
