I haven't heard Seventh Star, but I've heard the Martin-era from Headless Cross through to Cross Purposes (and a couple tracks from Forbidden). I can't say I'm a big fan of it. Cross Purposes, and the Forbidden songs I've heard, were okay, but Headless Cross and TYR are downright cringeworthy for me to listen to. Sabbath trying to sound far too "epic", for it's own good, IMO.
But then again, my opinion might not be the same as most; I though Heaven and Hell was a shit CD, apart from Neon Knights and Die Young (a near perfect song in it's own right). I thought Dehumanizer was much better.
I much prefer Ozzy and Ian Gillan Sabbath, as well as Dehumanizer-era Dio Sabbath. I think my three favorite Sabbath albums have to be Sabotage, Born Again, and Dehumanizer.