Log off and don't log back in until you've heard Master of Reality, Sabbath Bloody Sabbath, Sabotage and maybe Paranoid in full.
FTFY.
Don't care about Ozzy, the albums with him are much more interesting musically. The Dio stuff… is mostly Rainbow/Dio with Iommi and Butler included, which is great, but... I still prefer Rainbow.
My list of albums to listen to is already long enough. The only albums from Sabbath I'm remotely interested in hearing at this very moment are the really deep ones without Ozzy and Dio.....
...and you
haven't heard those with Ozzy and Dio… Why would you do that? Apart from some hipsterish "I like and listen to the unpopular albums only" bullshit, that is
I'd recommend not doing that, because… well, I
can enjoy
Eternal Idol or
Cross Purposes and the insane idea of Sabbath with Gillan or Hughes makes me even appreciate
Born Again and
Seventh Star a bit... but those albums are forgotten for a reason. I know they have their supporters, but just as with Aerosmith - those first six records were so special it's always tough to try to live up to that. And yeah, Ronnie managed to do so for most, but he kinda turned them into a completely different band.
But hey, whatever. Do as you please, but you're really missing out on at least
Sabbath Bloody Sabbath and
Sabotage. And I'm saying that as someone who used to hate Sabbath (and Ozzy even more) and those two albums plus
Master of Reality got me out of it.
EDIT: Also, for what it's worth, I
reeeeeally don't consider Sabbath in any incarnation a "classic heavy metal" band (okay, maybe the Martin era). Leave that to Saxon or someone like that.