I've given this brand of literature a wide berth.

Ah, that kind of snobbery. I see where you're coming from...

Fantasy fiction has always struck me as the slower kid brother to the more thoughtful and mature older brother of science fiction.

I don't buy this analysis at all. In fact I don't really see much difference between the two, except in aesthetic terms. Both can be just as inspiring, just as thoughtful, just as mature and just as interesting. They just have a different aesthetic appeal. Science fiction is simply a sub-genre of fantasy writing.

but, it seems to me, fantasy looks inwards and tries to create worlds within our own, whereas science fiction casts its gaze outwards towards the stars, both literally and metaphorically.

One could, by that logic, condemn human biology as a discipline because it is not astronomy. I don't see why the traditionally spacefaring settings of science fiction should somehow make them more worthy or worthwhile than the traditionally historically- and mythologically- inspired settings of fantasy works. What has being set in a fictional place a long way away got to reccommend it? The narrative and character and ideas are not made more compelling simply because they are imagined to be light-years distant.

If challenged to recall an image from sci-fi that has entered the public consciousness, you might think of William Shatner kissing Nichelle Nicholls in the racially-charged 1960s, the doo doo doo doo doo of Close Encounters, or Chuck Heston screaming "you maniacs, you blew it up. Damn you all to Hell". And these are just a few. Try the same thing with fantasy and you might get the image of Arnold Schwarzenegger in a pair of sandals.

If we're just sticking to the cinema then there's a lot. What about Ray Harryhausen's iconic animated skeleton warriors in Jason and the Argonauts? Or the menace of Christopher Lee's dracula? Or the haunting schizophrenia of gollum in the Lord of the Rings trilogy? But it goes deeper than that. Fantasy literature trades on archetypes, on deeply-held cultural tropes. It's almost Jungian. We are all familiar with the crusading knight, the barbarian warlord, the massed army, the wise sorcerer, the mighty dragon. Indeed, science fiction often borrows from these fantasy archetypes to achieve its effects. Star Wars, after all, has its share of knights and princesses, hermit-sages and evil emperors and swashbuckling adventurers.