For me, Korean sounds the best. It has enough vowels to let it sound smooth and when I was in Korea for two months, I literally just sat in cafes alone to listen to their language. It was that good! It is like those romance languages but, an asian one haha!

Japanese was one of my favorite languages before I heard Korean.. I came to realize that the language was too light and there was really no "fun" in the language... But it still is one of the most beautiful languages!

Mandarin was really weird to me at first but when I got used to it, it sounded alright with all the rolls in sentences... like sherrr lol...

Cantonese... no offense... but I really don't like... this language.. I mean I tried liking it.. I tried and tried and tried but it is just.. too harsh.

Btw I am austrian :-)