The heyday of hard rock and power metal in terms of mass commercial appeal. Anyone who was someone was playing arena and stadium shows in the day. And sadly, those days are gone forever.
When rap came on the scene some 25 years ago and helped to push metal off the airwaves (along with grunge), I thought it was just a fad that would burn out in a few years. But it's as strong as ever today, even though they prefer to call it hip-hop instead.
History is far overdue to repeat itself in the music industry.