I agree with you when it comes to Sabbath - as much as I love the 'Sabbath Bloody Sabbath' album, I've never understood the fanboy devotion that the Ozzy-fronted lineup inspires ...
Fanboy devotion? You might as well say that about anyone who likes any band.
Simple fact is while I wouldnt call myself a mental fan, Ozzy fronted Sabbath was great and the only Sabbath for me. Heaven and hell was a good album, but sounded nothing like Sabbath. The rest of their career with whatever singer, just never sounded like Sabbath. Also at the time they came out, their sound was truly unique.
Master of reality was my proper introduction to the band, and considering my influences were the likes of Poison and Guns N Roses etc, there was no reason I should have liked them, but I loved that album. If that makes me a fanboy, then so be it.
By 'fanboy devotion', I mean the people who blindly worship everything put out under the 'Sabbath-with-Ozzy' banner (I agree that the same could be said for any band) ... I like a lot of the Ozzy-fronted material, but I don't automatically start dribbling the minute the 'classic' line-up is mentioned.