That's interesting. I've always liked the sound of Swedish - it reminds me of Italian for some reason. But yeah, I can definitely see how learning a language would make you appreciate it more. Maybe my theory isn't so water-tight after all!

I read somewhere that people tend to prefer the sound of languages that have few irregular sounds. So one reason that languages like French, Spanish and Italian tend to rate so highly is because they have a narrower range of consonant and vowel sounds than most other languages, and also don't tend to have guttural sounds, which people usually dislike. The sounds they do have are also often found in other languages. And so when they're being spoken, people like the sound of them because they hear some familiar tones they like, but not any unfamiliar sounds they don't like.