Are we presuming that the DM is writing his own dungeons, and not using prepackaged ones?
I've had long running games that weren't in D&D, such as Cyberpunk or Call of Cthulhu. Those campaigns have mostly used published material, though. So I think availability of materials definitely enters into the equation.
The core game certainly does make a difference. A lot of games I've seen without a solid core quickly lost their way; once you did the two obvious things in the setting, there wasn't really much else. Or, they assume the same core as D&D but either don't support it or can't do it as well.
One thing that might make a difference is that the core of D&D is so familiar- not from literature or whatever the "story games" are trying to ape, but from game experience itself. Miniatures, battlefields, and the like aside, the dungeon is essentially a wargame or board game play experiences. You move into a square, deal with what is there, and move to the next square. It's something we all know from childhood, and that we can get into automatically, without getting hung up on "realism".
When other games start branching off into story-heavy elements such as negotiations, intrigue, etc, I think they often miss their version of the familiar experience. In many ways, it seems that this is still being worked out within the hobby. We know what a dungeon game is, but defining other types of games is difficult (see any thread on "railroading"). So a game that keeps it's core principles in mind is going to be better off.