Bob Dylan gets all the credit as his generation's great wordsmith, but Joni Mitchell's lack of ego with regards to titles shouldn't overshadow her obvious gifts. Maybe the first songbird [sorry Anne Murray! later Mariah!], but definitely the first lyricist to craft scenes that could accurately be called painterly and cinematic. She could also render the micro macro, and the small-scale heartbreak of songs like A Case of You still register. Q-Tip said it best - "Joni Mitchell never lie."
Ballpark anthems, written in major keys. Messiah complexes. Journeys of men stuck halfway between the gutter and the stars. All foundations of modern rock, all courtesy of U2.
Seriously - try to imagine the past thirty years of popular music without them. Can't be done.
Next: Kylie covered them on her last tour! Quick - get thee to Wikipedia!