You very well have a notebook filled with game ideas. Stranger things have happened, certainly. Sometimes you have a pet idea that you keep telling your friends and colleagues about (an idea which they are likely tired of hearing you talk about).
One of mine has been "Reverse tower defense". I should probably make it clear that I don't think I'm brilliant or anything like that for merely adding the word "Reverse" in front of a well known game design paradigm. But today I came across this: http://store.steampowered.com/app/91200/
Sometimes it's nice to know that our ideas are at least considered viable by others working within our same space. And while I haven't played this game yet, it does look like fun. If it turns out not to be fun, the trailer at the very least makes it seem highly likely that it could be fun.
This also touches on the concept/reality that these ideas are out there to be discovered. Your ideas, by themselves, are not special. Do not allow yourself to flirt with arrogance and narcissism.
What is "Special" is that you could take the same idea and 3 people and have them execute on it individually and achieve varied and nuanced results. That's where your quality [hopefully] is. If it's not, then no idea was going to save you from mediocrity.