... I would offer Neal Stephenson as an example of a fantasy/sci-fi writer who broadens your horizons. However, he's not writing worlds with, as you put it, dragons and elves and fairies. His fantastic elements tend to be a fair bit lighter than that, which I think might be something you talked about earlier. I haven't been reading every post. For the record I think that you are right that people could (and perhaps should) be broadening their horizons more, but I also think that many (not all) of the books you and Larry promote as mind-broadening are actually dull as dirt. That's probably just a matter of personal taste.

But back to Neal Stephenson. You'll typically find his books in the fantasy and sci-fi sections because of the light fantastic elements within them, but as he tells stories he teaches about topics such as history, economics, cryptography, mathematics, and dozens of smaller topics that catch his interest. His books are full of well-written asides packed with factual information. You can learn quite a bit from them if you want to.

For the sake of continuing argument, there are several fantasy authors/books that can teach you a little and give you a greater interest in particular topics. Neil Gaiman's books are full of real-world mythology, for example, and his Sandman books are also sprinkled with factual history lessons.

Fantasy and sci-fi writers can also be effective social commentators, which is another way they can broaden the mind. I suspect that science fiction has more of this, but I don't read a lot of it so I can't say for certain how good it is. Matthew Stover's Acts of Caine books are a blend of fantasy and science fiction that have at their core a social commentary on class systems and the culture of entertainment. China Mieville's fantasy novels also contain quite a bit of relevant social commentary.

However (again, didn't read all the other posts) I suspect you're talking more about standard, run-of-the-mill fantasy, where of course you're correct that there is not a lot of practical relevance to the real world. That doesn't mean that there can't be emotional relevance, because every fantasy world, no matter how run-of-the-mill, also contains things such as personal interaction, relationships, basic social structures, etc., that do indeed happen in our world as well, and can be of use to people. It's not mind-broadening in the typical sense, but it's not worthless either. Well, it's not worthless in most books. Some of them are just so bad that even this stuff is worthless.

But I would also argue that the split in the speculative fiction genre between worthwhile/intellectually stimulating books and fluff books also exists in most other genres. The books written decades or centuries ago that became classics did so because they were of the first category, but there were thousands of books written, published, purchased, and enjoyed by people that were fluff. It's not a problem that's endemic to fantasy. There's fluff everywhere. There's fluff down every aisle of every bookstore.

If there's a case to be made against fantasy/sci-fi, I think it's safer to say that it has a higher fluff to non-fluff ratio partially because it appeals to young peoplea as an entry into literature and partially because it's a younger genre in general. The longer it percolates in society, slowly more people with intellectual ideas will write stories in it, and the more non-fluff we will get. But there will always be fluff, just as there will always be a Dean Koontz and a Danielle Steele in the "real world" novels.