I completely understand your point, maybe I did not explained it adequately.
Nope. An idea is just a piece of the whole picture. Take the wildly successful Halflife game series: You're a scientist with a crowbar in a underground labratory overrun with aliens and soldiers trying to kill you. Many other games already had that "idea", but Halflife's gold was how it was executed. Take World of Warcraft: You are in a fantasy world. With orcs and Elves. And you have swords and magic. And it's online. Sound like every other MMO out there? Yep, but they executed it way better then their competitors at the time of their launch. Modern Warfare: Have guns, shoot other players. Billion dollar franchise. Because of quality, not idea. Halo: Have guns, shoot other players. In SPACE! With aliens! Billion dollar franchise. Because of quality, not idea.
Mario: Consistently high level of quality = long term success. Billion dollar franchise. Spyro the Dragon*: High level quality degraded over time = No longer much of a success. Banjo Kazooie: High level quality, degraded over time = No longer much of a success. Sonic the Hedgehog: High level quality, degraded over time = No longer much of a success.
I'am NOT placing only the basics of the game. Like I explain what the game is about and that more or less about it. In my GDD I do everything. Lets take the World of Warcraft as an example: I write the story line, I make the races, the classes, the zones, the quests/tasks, the talent points, the skills - I make a name for the skill, I explain how it looks, what kind of sound the usage of the skill makes/what sound it does on impact, and I do complete maths.
Basically, if you take my GDD, you don't have to ask What kind of enemy is supposed to be here? What is his name? His attributes? How he will react? etc. etc. You just write the code.
I don't know... I just think this is the most important, the most valuable part in the game development. Yes, there is the hard work of coding, recording the music, creating meshes, textures etc. but someone have to bring the in "the game" in the first place, or not? You also cant make a good movie without a good script. You cant write a good book without a set of ideas.
If I come to a prestige novel writer and tell him: "Look, I have an idea which will yell another Lord of the Rings or Harry Potter success." (And I'am actually not lying and it really does have the potential). Even if its only an idea and HE is the one who have to write it, can and will he just send me to hell? I don't think so.
You think that even if the idea is unique (and I mean really unique) - nobody will want it only because "It is just an idea?"
I mean, isn't it all (games, novels, movies, etc.) just and only about the prime idea and the rest (the actual work - programming, art, music, sound effects, etc.) can only "boost" or "kill" the quality?
Additionally, Isn't a good GDD also the part of the overall work on the game? I spent hundreds of hours writing my GDD and its now more then 4000 pages.
Also, it contains the story script, art concept and notes for the music.
And of course, I can go with much less then 50% of the profits. Why it cant have at least a minimum chance to succeed?