Ideas are worth more, I make millions selling my ideas.
Was this sarcasm? Because I doubt that very much.
I really think the old Thomas Edison maxim that Genius is 10% inspiration, 90% perspiration, holds true for game development just like almost any other art form :).
It’s too bad that his ideas were 90% inspiration (from Tesla). That is a very good quote to describe the ideas vs engineering argument, though.
You forgot Pooyan (playable!)
And, of course, the EU release of Hudsonsoft’s very first iteration of their Bomberman franchise. Dating to the early '80s and released on the ZX Spectrum and MSX, it was sold under the name “Eric and the Floaters” in the EU for obscure licensing reasons. (There were some other games with names like “Bombo” and “Bomb Jack”, so they may have simply changed the name to make it stand out.)
Both games involve balloons, yet both games are also completely different.
Haledire is correct: a simple idea is not enough. You have to create a complete game and that means drilling right down into the details.
“Balloons!” is insufficient as an ‘idea’. I wouldn’t even call it an ‘idea’: it’s more like just a random thought pinging about one’s brain.
If someone came up to me and told me about their awesome idea for a novel—“It’s a story about balloons!”—what would I say to them?
Assuming I could resist the temptation to tell them to go away and leave me in peace, I’d ask them for more detail: For more information about what role the balloons play in the story; what the story is really about; who the characters are, and so on, and on, and on. A few paragraphs on coloured balloons rising majestically into the skies of Pratt’s Bottom will not fill a 120000-word book.
Game design and development is all about having thousands of ideas, writing them down and seeing how well they work together. Some will gel. Some won’t, and will need to be ruthlessly expunged. That’s why we make prototypes and testbeds. A gameplay mechanic comes from ideas about how the game will be played. A character comes from ideas about what kind of character would fit the game’s environment.
So, yes, ideas are where it all comes from, but the ideas alone are of little value. Being able to provide ideas is not a skill of any great value. Anybody can provide the sand of ideas. It’s only when the sand is combined properly, and in the right proportions, that you get concrete. Game developers aren’t in the business of selling sand. They’re in the business of selling concrete. Games. The end result of combining all those grains of thought.
Balloons ? 
Good god, I forgot all about “Pang”! (The image isn’t showing up, incidentally; I have to right-click and open it in a new tab. [Update: But, bizarrely, it appears just fine in my quote of your post!)
Bloody difficult too.
Honestly, kids these days. You tell 'em about games about collecting trash, or cleaning up after a particularly wild party, and they don’t believe you!
Harrumph!
Actually, this is a misapprehension. You can sell your concept to publishers when you´ve worked succesfully with them in the past.
It all comes down to confidence. But you´ll need a track record and you must know the habits and preferences of your publisher.
The idea is used to get the attention, the concept is used to nail down the contract.
For me ideas are the first reason to get started, so they are really valuable to me.
My understanding is not exactly that way.
I would rephrase that to:
You can convince your publishers to let you work on what you want when you´ve worked successfully with them in the past.
It all comes down to stubbornness and how much money you made them earn in the past . But you´ll need a track record and you must know the habits and preferences of your publisher, and be very very lucky.
Of course your idea has to fit into their portfolio. They won´t let you work on what you want while they throw money at you.
Normally it used to be like that: Phone rings, I pick up and they ask me if I have something for them. Then I tell them about my rough ideas and if something sounds good to them, they ask me to write a concept. This concept is the base for the contract.
That. To my knowledge, there has never been a instance of a publisher literally buying an idea written down in a document from someone and nothing else, even if they had a proven track record. There are design directors, who are always ex-programmers, like shigeru miyamoto and cliff blesinski, but they still do a lot more that just kick back in a chair and come up with ideas.
Generally the best ideas are also coupled with an great idea for the implementation. John Carmack had an idea for a competitive multiplayer fps, but he also had an idea as a programmer of how to implement it so it was smooth and responsive regardless of latency, and it pretty much changed the industry (client side prediction - quakeworld).
raise hand
Edit: For three times, to be more precise.
Right, and I’m John Carmack.
See? Anyone can make stuff up on the Internet 
1: http://www.simuwelt.de/game/sportangeln-2012-suedeuropa
2: http://www.simuwelt.de/game/untertagebau-simulator-2011
3: http://www.simuwelt.de/game/garten-simulator-2010-73
WIP:
http://www.indiegamedeveloper.org/?page_id=97
Edit: See, exceptions prove the rule.
Yep, those sure are some games. Where’s the part that proves that someone cut you a check for writing “Garden Simulator” on a napkin?
I think you have to believe me in this case. Why should I lie when it comes to this?
All I want to say is, that it´s not the holy grail to sell a concept, based on an initial idea.
The thing is, that the idea opens the door.
http://www.indiegamedeveloper.org/?page_id=90
It says you were contracted to design, program and produce. So in which place are you lying? Did you sell them a GDD, or did you write code? Sounds like they contracted you to make a game. They didn’t just buy an idea and nothing more.
Regardless of “what you wanted to say”, my original statement was pretty clear, and you claimed otherwise: “there has never been a instance of a publisher literally buying an idea written down in a document from someone and nothing else.”
Sure, in the long way they contracted me to make a game. Let me quote myself:
I apologize for misinterpreting “nothing else” (I´m not that good when it comes to english).
We are in line when it comes to your original statement.
Though, my opinion stands: Without the idea, there will be no execution. They depend on each other, and they are both valuable.
Have you been hired for the duration of the projects? Because if so you would not just be “selling the document and nothing else.”
If you have, then you would be the first game designer I hear about that does not get to ride the full development cycle (not saying it’s impossible, just the first one I hear off.)
To be fair, in these forums, thats a question with a lot of references to justify why anyone would think some one would lie about this stuff. 
I give you the benefit of the doubt, though.