Reading some game books recently, it occurred that good game writing is technical writing, not creative writing. Good rules writing and good supplement writing, anyway.
Don't get me wrong. Creativity is important. It's critical for stuff for your own games and for making what you write worth reading.
But ultimately when you're writing game material for publication, you're trying to write a set of rules or encounters or fluff in a way that useful to another person. It has to be clear, concise, well-organized, grammatically correct, and spelled correctly. It has to communicate the writer's intent and meaning first, and entertain second.
If you're planning to write for games, think of it as a operator's manual, not a novel.
If the rules aren't clear or the author's intent isn't clear you get questions, disagreements, rules conflicts, and important rules buried so deep in the text you don't know they are there. This is the "AD&D has a rule about helmets?" corollary. Or the endless wonder about how AD&D initiative really works.
This doesn't mean there will never be rules questions or disagreements if the writing is good enough. Rules might conflict in edge cases or even a well-written rule might be misread or misunderstood. In general the clearer the writing, the better. A well-turned phrase and a great idea is nice, but if you don't know how to play the game after you read it, it's not enough. It better be entertaining and interesting, but they can't do the job on their own.
In short, in my experience: Communicate first, communicate entertainingly second. Do both, but it works better if you keep them in that order.