Of course I'm not starting a campaign against being succinct (all evidence to the contrary); that would be absurd. The only issue I've got with the advice "be concise" is that it can keep writers focused on the clock or the word count, instead of the creative process. Every piece of writing should say no more and no less than what it needs to; the trick, as you mention, is deciding exactly what it needs to say. Where I'd disagree with your comment is in deciding what is superfluous:

Good storytelling is when every line in a novel, every scene in a play or movie is there only when it furthers the story.
I'd say that's efficient storytelling, not necessarily good storytelling. I need traffic signs and fire extinguisher instructions to be efficient; stories, I don't mind if they ramble. (One of my favorite writers is Roy Blount, Jr., and he wanders around, goes off on tangents and digressions, repeats himself, and somehow almost always manages to tie it all together at the end).

And many of my favorite moments in games have been the ones that don't really further any story, but are included just for the hell of it. A random comment or a joke, or some meaningless interaction like turning lights on and off or looking at random objects. You could go through some justification that say those moments are storybuilding because they develop character or they establish interactive parameters of the world, but that'd be pushing it. They're just there for fun.

The reason I think games have unique difficulties when it comes to this topic is because there's such a big push for the writing to be purely functional. Get in, give the player the minimum amount of information he needs to continue, and get out; the real artistry of a videogame is in the game design. I say there's room for artistry everywhere, as long as it all works in concert and there's no one part that detracts from everything else.

So I say the best advice for videogame writing is the same as for any other type of writing: not "it should be short," but "it should be short when it needs to be short, and long when it needs to be long."