My monthly AD&D campaign has confirmed something I suspected after observing my two 4e campaigns.
I am not a storyteller. I do not like establishing plots or events before we sit down to start playing. I like drawing maps and making notes about what lives where and why. I like sketching out NPCs. I like putting together fictional environments with all sorts of events on the verge of kicking off. But I don't actually like writing about those events, and I'll gleefully hack things to pieces and rearrange them to suit whatever idea pops into my head.
I am the god of this tiny, virtual universe, and if I decide at moment the characters enter the dungeon that there are three-headed kobolds there instead of the cyborgs I wrote about in my notes, there's no power in all the cosmos that can contradict me.
I DM because I want to see what will happen next, maybe as much as the players. Hell, probably even more than them. That interplay around the table, the unraveling of plans, the sudden bursts of inspiration, all of those things are what keep me coming back to the table.
That probably also explains why my #1 pet peeve is a player who quotes rules to me. Think the rulebook has all the answers? Then let's see that rulebook run a campaign!
The AD&D game really brought this all home to me. It's been a lot of fun, in part because I didn't take it all too seriously. It also helps that I have some great players. Erik Mona is a roleplaying MVP in my book. He's exactly the kind of player I like having at my table. His character is always doing something interesting, even if Stephen's character keeps murdering the NPCs he tries to interact with.
On another note, playing AD&D has been an interesting experience. I've found that I run it much like I did back in the day. The players use the character options from the Player's Handbook, I use the monsters and magic items from the DMG, but the rules I use behind the screen are basically OD&D/BD&D and lots of fiat.