1. The Original Ozzy Era (1968-1977)
With apologies to the late, great Ronnie James Dio, Black Sabbath created their best work with Ozzy Osbourne in the early 1970s. The Birmingham group came together as the Polka Tulk Blues Band in 1968; that soon changed to Earth and, finally, Black Sabbath. Their self-titled LP in 1970 pretty much invented heavy metal, an art form that they perfected later that year with the release of Paranoid. The band toured and recorded consistently through the late 1970s, though a steady diet of cocaine soon led to a disappointing string of albums before Ozzy Osbourne left the group (very briefly) in 1977.