Um, I do disagree here. Most early modules were pretty bare bones as far as content. Go to this place, kill everything there, take the treasure, go home. Not a whole lot of other stuff going on really. Whether it's Against the Giants, or Slave Lords or Isle of Dread, there just isn't much content at all. Mostly dungeon crawls filled with static encounters (yes, yes, there's more, but, I'm painting with a broad brush here).
But, it was the presentation that really drove these things. Whether it was the art packets in modules like Tomb of Horrors, or fantastic cover art, or some pretty interesting descriptions of different situations - bree yark and all that.
I mean, heck, we've got sites like Canonfire for Greyhawk and Candlekeep for Forgotten Realms for a pretty good reason - all that flavor stuff. We've got thousands of pages of setting guides that give virtually no actual adventure situations, just descriptions of an area. Inspirational for adventures, sure, but, not adventures themselves.
Pathfinder has built an entire line with Golarian based on the notion that presentation matters. Half of the material they put out for each adventure path is setting background. I'd say that the literary is pretty darn important to the hobby.
But, since we're apparently not allowed to talk about RPG elements using literary criticisms, we are then forced to create entirely new ways of discussing how we play RPG's.