I thought Bark at the Moon was a great album. I thought the highlight songs were really good. And the rest of the album, whether you want to call it deep cuts or filler, was also really solid all the way through. It was definitely an album where, for my tastes, I could repeatedly listen all the way through without losing interest, which is something I canNOT say about a lot of albums from that era.
The Ultimate Sin, on the other hand, really felt uninteresting to me. A friend bought it first. I listened, and it just didn't click with me at all and didn't feel nearly as strong. Although it had a handful of catchy songs (Shot, the title song, and Killer of Giants), none of those really felt compelling to me. And none of the deep cuts stood out.
So yeah, Tim, I'm with you on Bark at the Moon being FAR superior, at least for my tastes.
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As far as the entire discography, it's hard to rate. As I kind of mentioned above, I got into Ozzy as one of the first real hard rock bands that started to form my tastes in that sort of music, but he then became a pretty big turnoff. I got Blizzard of Oz very early on as one of my first hard rock albums, and I listened to it to death. Great album. I then got Speak of the Devil because it was one of the only two other albums available on Columbia House at the time. I listened to that album a TON while on my paper route as a kid. So both of those albums burned into my brain. That would be followed very shortly by Bark at the Moon, which got the same paper route treatment. If memory serves, I caught up and got Diary a bit after that. And for whatever reason, just didn't listen to it as much, even though I recall it being pretty good. After that, Ozzy just lost me. When No More Tears came out, I really liked that one as well. But that was pretty much it for me. Nothing afterward clicked. So those five albums are really the only ones I was every really interested in. Ranking them, I would probably go:
1. Blizzard: I'm not sure it is the "best." But it holds a special place for me.
2. Bark at the Moon: Gets the nod for the #2 spot for just being so solid and consistent.
3. No More Tears: The title song is, IMO, far and away the best song Ozzy has ever done. The rest of the album is good. But not nearly as many standouts.
4. Speak: Really good live performance of those Sabbath classics.
5. Diary: I remember it being pretty good. But I don't remember much more than that.