hey, I'm french and don't understand 90% of the lyrics of the music I listen to (moreover when the lyrics are screamed), of course I can read the booklet etc etc, but most of time this is american argotic, so even if I do my best, I still don't understand 90% of it...
About french music, well, first there's not a lot of good french music. (I don't know why, I just feel like english sounds better than french, for singing particularly, or maybe it's because I don't understand the stupid lyrics !), and if lyrics are not good, they at least can be funny... Well, at least one half second... So personnaly I don't care about lyrics, as long as it's not racist or anything like that.