I can't ignore what Sabbath with Ozzy di for Hard Rock/Heavy Metal.
I like most all of Sabbaths work...but Heaven and Hell and Mob Rules are my two favorites.
I really liked the first few Ozzy solo albums, but after that it got repetitve to me and I was done.
I've enjoyed DIO from Rainbow to present.
It's close, but I have to give the nod to DIO over the course of a career!!!