Ideas for games are not at all scarse. They are not at all hard to come up with. They are not at all unique. In fact, ideas for games are much more trouble than they are worth. Game developers don't need any more ideas. The only way to ship a game on time is to brutally throw away as many ideas as you can, until you have the smallest design that will actually work and be fun, and then EXECUTE on that. Execution is wh…
You hint at one of the other issues that arises. So much of what a piece of software becomes (game or otherwise) is formed as it's being written. Something sounds great, you implement it, it doesn't look so good but leads you to something else, etc. In the end the game might end up being 50% of the original and 50% from prototyping.
One of the things that gets me is the person who says "Implement my idea. I don't have any money to pay you but you can have a percentage of the profits". Is there a single word that means naivete + ignorance + hubris? This is especially true for those who say they have a great idea for a game, but don't want to tell you because they don't want you stealing it.