Black Sabbath, the Ozzy version, wrote the rule book for heavy metal. From the first album to Sabbath Bloody Sabbath you are talking about 5 of the greatest albums in heavy metal history. I love Dio. Personally believe that his work on Rainbow Rising is as good, or better, than Heaven & Hell, which is a very good album, as well.
Give me Ozzy and the original Sabbath line-up any day. Wheels of Confusion, Children of the Grave, War Pigs, Sabbath Bloody Sabbath, NIB . . . are you kidding me!