1. Heroes in these stories may attempt anything.
* John Carter literally wills himself from a civil war battlefield to Mars and back...
2. The setting and scene are subject to the whims of the narrator...
...If anything, the core mechanic of 4th Edition is the **perfect** abstraction to make such a setting relevant again. Players can try to do anything; just roll a d20. The DM may do whatever he wishes to the setting, verisimilitude be damned; just add and subtract modifiers and set DCs as you wish.
What issue of The Sandman is it? Morpheus is in hell attempting to regain his helm, but must challenge the demon who possesses it to a game of Reality.
"I am a dire wolf, prey-stalking and lethal-prowler"
"I am a hunter, horse-mounted and wolf-stabbing"
"I am a horsefly, horse-stinging and hunter-throwing"
"I am a spider, fly-consuming and eight-legged"
etc.
Later in the series it is called "the oldest game"...anything can happen on Oerth. Because more than in any other module or source book, Castle Greyhawk demonstrates that heroes can try anything and the setting is clearly subject to the whims of the narrator. It is a tautology, but because of this Greyhawk is the most "D&D-ish" it is the best of any setting.