Def Leppard was actually one of the first true rock bands I was ever exposed to, thanks to an older brother who was a big fan of theirs during the Pyromania and Hysteria eras. Even as a kid, I could see the appeal of the music--I will maintain until my dying day that if the Leps aren't the best rock band ever, they're at least the most accessible. And they literally changed the whole face of rock music during the 80's; without them... well, I probably can't say that a great many of my other favorite bands would never have existed, but they might well have looked and sounded very different.
I have to veer off on a tangent here for a moment, and say that I don't really like slapping labels on music or artists except in a very, very general sense. I mean, obviously there's a huge difference between contemporary and classical, for example, or country and new age; without some kind of labelling, we'd all be wandering around totally confused. But when it comes to pop and rock, the division is much less clear, and it seems kind of stupid to me to completely write off one genre or the other. I like both, and I don't make any excuses for it. From my own perspective as a fan, there just really isn't any question of which is more "credible" or "valid;" it's a non-issue. I like what I like, simple as that.
I also have a certain fondness for things that straddle the lines between different genres, in all forms of entertainment: books, movies, TV shows, etc. It's just cool to me when someone can take the best of two different things and mix them up together in a new and interesting way--perhaps because that's what I often end up doing when I write. And that was also pretty much what Def Leppard did with music; they were the first band to blend elements of heavy metal with the slick production of pop, and the record-buying public loved it. Their Pyromania album was, in essence, the blueprint for both a new kind of band and a new kind of music, and in between 1983 and 1987, dozens of other bands tried to emulate that same winning formula. Naturally, some got it right, and others didn't--and yet, when Hysteria came out in 1987, I think it was clear that nobody did Def Leppard better than the Leps themselves; that album broke all kinds of records for sales, concert attendance, hit singles, etc. (And, just as a trivia note, Europe opened for them during a portion of the American tour--boy would that would have been a show and a half!)
From a personal perspective, though, I think the most telling indicator of how good a band the Leps are is this: The album after Hysteria, called Adrenalize, was supposed to take only a year or so to record, but due to a combination of bad luck and the tragic death of guitarist Steve Clark, it didn't see a release until 1992. Musical fashions had changed by then; grunge was the up-and-coming thing, and the Leps' brand of rock was beginning to be considered passé--yet Adrenalize still sold six million copies and had several hit singles. It might have been the "last gasp of the 80's," so to speak, but if any band had to do it, at least it was one who really deserved that final shot of success. For Steve's death was, of course, not the first tragedy the band had weathered; the other was when drummer Rick Allen lost an arm in a car accident on New Year's Eve, 1984. As someone who has a tiny, tiny bit of experience at drumming (I played in my high school band for a year or two) I am just in awe of that man--there are probably not a whole lot of people in the world who could have something like that happen to them and not let it stop them from going right back to their chosen career.
Still, despite that admiration--and the fact that the whole band is amazingly photogenic--it was Joe Elliott who really caught and held my eye when I got old enough to appreciate the Leps in ways beyond the musical. I'm pretty sure that "Pour Some Sugar On Me" was one of the first music videos I saw when I actually started watching MTV, and what a way to start... (Another trivia note: That video was actually shot right here in Denver, at the now-demolished McNichols Arena. Too cool!) I have the feeling that seeing all those women in the audience, straining and screaming towards Joe--who was looking hunky indeed in his ripped-up jeans and tank top--might well have been my first clue that I was not the only one in the world who thought musicians were the sexiest things on two legs! And even yet, he's still very much worthy of admiration; the man has the most amazing eyes, and he's even still got long hair! And technically adept or not, I love his voice--he's another one who can just send shivers down my spine. (Though I do have to admit, he's probably the cause of more misheard lyrics than any other artist... sometimes I just can't make heads or tails of what he's singing... )