I've been playing some more 'modern' or story gamish games recently - things like Blood & Honour, Unknown Armies and Burning Wheel. One thing you notice about modern games is that they all tend to be 'about' something. They're not just tabletop games that you play to have fun. They're supposed to enable you to explore certain deep human emotional themes. Thus Burning Wheel is 'about' having your beliefs challenged; Blood & Honour is 'about' how obsession with honour leads to tragedy; Unknown Armies is 'about' making sacrifices for the pursuit of knowledge; Changeling: The Lost is 'about' finding onself after personal tragedy. And so on.
I think there's a tendency to contrast this with more trad games like D&D. You find this on both sides of the old school/avant-garde divide, so OD&D grognards poo-poo story games because "it's about the game, not the narrative" and story gamers poo-poo OD&D because it's "incoherent" and doesn't have a goal. Both sides perpetuate a supposed gulf between the two different play styles.
Au contraire. I think D&D is actually 'about' something too, and moreover, it's about something very specific. What it's about is ambition.
What else could it be? PCs begin at 'level 1' and hope to progress upwards to level 9 or 20 or 36. They progress upwards by gathering ever more wealth and doing deeds of derring-do of ever increasing magnitude. They learn new abilities and magic spells. They behave avariciously, whether in terms of wealth, power, or experience, and are never satisfied with what they have. Their goal is almost universally to dominate the world, even if this is usually unspoken, because world domination is implicit in their drive to succeed.
Ambition even seeps into the metagame, because in my experience it's generally only in D&D that you get DMs doing the crazily obsessive worldbuilding which you find all over the blogosphere and which I also engage in with so much gusto. You don't get people DMing Unknown Armies and coming up with the gargantuan folders stuffed full of random encounter tables, maps, random treasure generators, weather and climate charts, new monsters and NPCs, and campaign notes. You don't get the almost megalomaniacal ambition of a true D&D DM to catalogue an entire world in other games. Or, at least, not at all as commonly.
D&D is about ambition, greed, power, and the will to win above all costs.