Rothe said:
I wouldn't agree with GMless play. What does he mean by story? ...
What I thought he was saying is when you approach a cooridior player 1 pipes in "OK this corrdior has a trap, I'm going to disarm it and if I succeed I find a +1 sword." That I wouldn't care for as a player or GM. ... But there is no surprise or sense of discovery if I as a player define the obstacles ahead of me, and even worse if I assume the outcome of them to the extent I think Ryan is suggesting.
Just FYI, there are actually games that work this way (Donjon, for one), and they're pretty fun. By which I mean, they allow you to modify the game world, not that they let you define all the conflicts and fiat all the outcomes -- obviously that's never going to be fun.
Many more games allow you to narrate in minor changes with a successful roll or expenditure of a resource.
One thing that may be tripping you up is a focus on the imagined environment as "the point" of the game. I've been in lots of games where the scene details are changeable by the players (for instance, a Zelazny-style
Chronicles of Amber game where you could, in character, say "I round the corner and find a magic sword"), and those games still had interesting conflicts. You just didn't make the stuff you could do "effortlessly" the focus of the conflict.
I see that you prioritize things like "surprise" and "sense of discovery", so it sounds like a coherent imagined game-world is important for you. In that case, think of co-DMing as a situation where each of you play a "name level" PC and a lower level character, and when it's your turn to run things, your high level PC sets up situations the other players' low-level PCs have to deal with. That allows for collaborative story creation without jeopardizing the imagined fidelity of the game world.
But generally, collaborative-narration games work because their design allows for it. Straight-up collaborative D&D where the player is also the DM doesn't work, because it's not designed for that possibility. Or to try to sum up a too-long post, yes, if the game's about killing things and taking their stuff, you don't let the players handle that part. But if it's about something else, they could.