Truth be told D&D doesn't model MOST fiction well.
On this, I think it depends what you mean by "model fiction".
My own experience, plus a bit of reading around, suggests that it is very hard for RPGing to deliver the overall narrative pacing of a novel, play or movie. The following is from Robin Laws' "Hamlet's Hit Points" (p 12):
Theater and film, including off-shoots like radio and TV drama, serve as our strongest models for the RPG experience. Their emphasis on dialogue and external action makes their techniques ripest for our looting purposes. However, texts for playwrights and screenwriters don’t necessarily focus on our issues. Screenwriting manuals tend to focus on structure . . .
The improvised, collaborative nature of the [RPG] experience frees us from the tyranny of structure. We not only forgive messiness, we expect and demand it. Without it, players fear a loss of control to an overbearing uber-narrator. If, as GM, you can occasionally build on a previous moment in an unexpected way, cut out a few boring bits, and have something big and exciting happen near the end of a session, you seem like a genius of structure.
With loose structure being the norm, we can instead turn our attention to the moment-to-moment transitions inside a play, film, or television episode.
When it comes to those moment-to-moment transitions I think it is possible for RPGing to resemble fiction.
And when it comes to character motivations, and the ways in which characters drive the fictional events, I think it is possible for RPGs to resemble fiction. A character like Conan poses a degree of challenge because he is so close to being infallible and invulnerable - but in 4e one way to have a go at it would be a high-Heroic to mid-Paragon STR/DEX fighter with a barbarian or warlord mutli-class.
But modelling the sorts of events that occur in a Conan story isn't that hard - I've had PCs defeated by magical enemies and regain consciousness in dungeon cells (a la "The Scarlet Citadel"), and not too long ago I ran a
Burning Wheel session with a wizard's tower inspired loosely by "Tower of the Elephant".
I think the most important techniques for making RPGing more closely resemble fantasy fiction are (i) avoiding hard fails, (ii) emphasising situation/conflict rather than exploration of the GM's world, and (iii) building that conflict around the PCs' concerns, rather than imposing purely external, merely procedural adversity.
