Why I like J-pop
Or any music in a non-native language, really.
The human voice is a decent instrument. When the vocals are in another language, you have the ability to enjoy the sound, without being distracted by noticing how trite or silly the lyrics might be. Even 'N Sync can sound pretty good to me if they're performing "When You Wish Upon a Star" instead of "Tearin' Up My Heart".
Other languages are a step above listening to pure gibberish. Though you may not know the rules of the language, there are still constraints and commonalities different to each. The difference between listening to Japanese singing and German singing is maybe like the difference between two types of guitar.
Being particularly a video game and anime nerd, though, it's the Japanese music which I've become most accustomed to enjoying.