I quote Gruff Rhys in todays Metro, where he's talking about why he likes songs with lyrics he doesn't understand:
"Arguably, it's the emotion and voice that's important in a song"
This is something that I've always thought myself. The most important thing is the tune that is being sung, and good lyrics are just the cherry on top of the cake - good lyrics are good, but not essential.
I'm fairly sure that there will be a lot of people on DiS who disagree with this though.