My friend recently loaned me a CD box set of the first 8 Sabbath albums. The first three or four were solid but it dropped off after that. By "Technical Ecstasy" and "Never Say Die" they just weren't the same. "Heaven and Hell" re-upped it. Ozzy was cool but Dio had the pipes.
I saw Iron Maiden back in April and they did extremely well considering they'd be a little older than Metallica. Especially Bruce Dickinson who still sings fantastically despite a recent bout with mouth cancer (cured thankfully). And they continue to put out great albums after 35 years. :)