The Dungeon is Fundamentally Different
Tuesday, Zak at Playing D&D with Porn Stars, in a post called Some More Nice Things About Dungeons says this:
This makes adventures based around the classic dungeon (and any interior space you use in a game which resembles a classic dungeon--a stripped-down Death Star, a Tron-like computery world, etc.) fundamentally unlike all other kinds of adventure.
I think Zak's nailing it in this post about what makes the dungeon gaming different from any other kind of gaming. It's a fascinating insight.
Every role-playing game uses some kind of constraints to manage what the player (and the GM) can and can't do. There are realism constraints (your regular-guy character can't lift a bus), setting constraints (can't harm the werewolf with regular weapons), fictional constraints (the local priest won't heal you because you called his god a two-bit faith healer last session), social constraints (the GM doesn't want you to leave town because that derails the adventure), and probably way more I can't think of right now.
The dungeon neatly rolls a bunch of the constraints of the game up into the simple fact that it has walls and corridors that you can't circumvent without a great deal of effort, and probably not even then. Notice that the structure of the dungeon acts, at different times, as a constraint of ever sort I listed above. It boils the adventure down to a small set of options so that those options can be highlighted.
And that's a big part of what's awesome about it.
I'm trying to keep this in mind as I prepare my dungeon mastery posts.