I think that the riff is slowly, but surely, making a comeback. In the underground rock and heavy metal scene, bands like CKY, Trivium, Clutch, Five Horse Johnson, Fireball Ministry, Lamb of God, Shadows Fall, and a great number of others are enjoying great success in their efforts to bring the riff into the twenty-first century, supported by those members of the old guard (Maiden, Priest, Megadeth, Queensryche) who are still going strong. Even in the mainstream, bands like Nickelback are making guitar riffs increasingly central to their music, while there is also a wave of retro bands like Wolfmother, Jet etc. who are harking back to the '70s tradition of songwriting.