Wikipedia defines ‘high fantasy’ as being fantasy set in imaginary worlds, and ‘low fantasy’ as fantasy set in the real world (or ‘a rational and familiar fictional world’) with fantasy elements. I think this definition is misleading. A story isn’t high or low fantasy based on whether it’s set in an imaginary world; low fantasy is an attitude.
If high fantasy is The Lord of the Rings, low fantasy is Conan. High fantasy is ‘shiny’ and over-the-top and often though not always optimistic; low fantasy is about low tech settings where life is short. Larry Elmore is high fantasy; Erol Otus and John Blanche are low fantasy. Monty Python and Terry Gilliam’s Medieval stories are low fantasy, with their emphasis on mud and blood and grass and grime.
If you look at trends in MMOs over the last 12 years, they’re basically a progression to higher and higher fantasy. Ultima Online, the first major commercial MMO back in 1998, had all the visual flair of a bunch of Renaissance Faire people running around in the woods of Michigan (it didn’t even have nonhuman races!), but Everquest, which overtook it in popularity, had more dragons and orcs and stuff, and in World of Warcraft, fantasy is almost indistinguishable from superheroes.
There are still some popular fantasy franchises which are more low-fantasy than high, like the “Song of Ice and Fire” series (an important character being murdered in the privy is definitely low-fantasy). But would anyone play a lengthy RPG or spend days in a virtual world if it put them at a *worse* situation than in real life—grubbing for roots, patching worn clothes, suffering leprosy and fighting off continual hordes of goblins?