I just came across Kulning and cannot think of anythign more sweeter or melidious.
That's a song though; not a very subjective way to choose a favorite language to listen to imo.
I'm reading the Malazan Book of the Fallen.
Every language on this Earth is unique and they all sound differently from each other. So, IMO no language sounds better than any, you can have a favorite but that doesn't detract from the uniqueness of all other languages.
My favorite language in terms of sound would be French. I can't explain it but I just love it.