Robert E. Howard was, in many ways, an unappreciated genius. He's appreciated more now, but I think one aspect of this genius is still frequently unappreciated, and that's his unique (at the time) approach to the setting design for his most famous stories, the Conan tales, set in the so-called Hyborian Age. In fact, part of what I now consider to be pure genius was criticized by friend and fellow Weird Tales pulpster H. P. Lovecraft. See, Lovecraft thought that Howard's use of "real" names was troubling; in a fantasy setting, the names should be made up. Otherwise, it's not fantasy, it's "real life" intruding.
Of course, Lovecraft was wrong on this. Much of fantasy, including plenty of what he himself wrote, takes place in the "real" world with fantasy elements tacked on. And there's no cultural resonance with these fantasy cultures. What does it mean to be visiting Karnathes, king of Celephais? I have no idea. Those names don't mean anything to me. They don't bring to mind any hint of background.
What does it mean, however, to be operating in Nordheim with an Æsir war-party who call on Ymir as their god? Well, clearly that brings to mind a host of viking-like associations... without having to actually be real vikings. One of the things Howard was specifically trying to do was recreate that cultural resonance that came with using real cultures, while simultaneously freeing himself from the shackles that are associated with historical fiction. See, Howard himself wrote that he loved writing historical fiction, however, he found the research associated with it to be a major time sink, and a frustrating side effect of having to do so. If he got the name or dates associated with some historical figure or stage wrong, he'd feel terrible when he found out, and his fans would also (at least some of them) notice it.
But... what if he created a setting that could have the best of both worlds? Like I said, the Æsir instead of the Norwegians? The Corinthians instead of the Greeks? The Aquiloneans instead of the Romans? The Stygians instead of the Egyptians? The Turanians instead of the Turks?
This was a convenient short-hand, allowing for highly fantastic stories that had, in many cases, a mythological or "Arabian Nights" like effect, where the cultures, names and locations were a convenient shorthand for the readers, but the author had freedom to take things his own direction. What if you wanted to have Romans and Vikings in the same setting? Well, historically you couldn't; they didn't overlap temporally. But in the Hyborian Age, this "calque" of real cultures into a fantasy setting does in fact, render the best of both worlds.
Here's an example of two "modern" settings that have done the same thing: Games Workshop's Warhammer setting of "The Old World" and neighboring countries, bears extremely transparently calqued real-world countries. Or, well, like Howard, they are sometimes a combination of "real" world and "legendary" world. Bretonnia, for example, is not just high medieval France, it's also the birthplace of the Arthur legends, and bears a strong overlap of Arthurian romance in addition to whatever historical elements were borrowed. The Empire is quickly identifiable as a kind of melange of the Holy Roman Empire and possibly also the Hanseatic League; yet very recognizably medieval German throughout. The Kislevites are the Cossacks. Araby is, unsurprisingly, Arabia, Nehekhara is ancient Egypt, Sylvannia is the Transylvannia of Stoker-esque literature. Norsca is Scandinavia. And so on and so forth.
Paizo's Golarion setting does the same thing. Taldor is the Byzantine Empire. Ossirion is Egypt. The Land of the Linnorm Kings are the Vikings. Ustalav is the Stoker-esque Transylvannia. Qadira is a combination of the Arabian caliphates and the Persian empire. And so on and so forth.
I've been fascinated with the ease with which this kind of setting design flows. It makes it extremely easy to engage players (of roleplaying games) or readers (of fiction) in a setting that feels familiar like this, and yet they are forgiving, and in fact demanding, of you putting your own stamp on it.
I'm equally fascinated with guys like Edgar Rice Burroughs and his Barsoom setting, who specifically set out to create societies of alien humans; people who had no link with any Earth civilization, and so wouldn't be expected to closely resemble any such civilization either. But I admit to being fascinated with them for completely different reasons. And I think that, especially for games, the former type, the "Hyborian Model" is the easier one to implement and get up and running.