Your game can not be one of a dozen if it never comes to light. Better to complete a project and have it labeled than to never produce one.
You can't expect original ideas to spring fully formed in your mind - everything is a derivative in one way or another. Metal gear's stealth mechanic was a combination of technical restrictions and Hideo Kojima having just watched 'the great escape', for example.
I keep a notebook that I fill with clippings, quotes and the occasional drawing and make a point to look through it all regularly - the idea is that come into contact with things you wouldn't normally think of in order to make connections that you otherwise wouldn't have. One example might be that you're designing a character and come across a picture for a carburator which gives you the idea to give that character a mechanical heart.
As it happens, in this book there are a few quotes which are relevant to your issue:
"to find the answer one must first understand the question"
"extraordinary products are merely side effects of good habits"
"the object of painting a picture is not to make a picture - however unreasonable that may sound.
The object, which is back of every true work of art, is the attainment of a state of being, a state of high functioning,
a more than ordinary moment of existence. The picture is but a by-product of the state, a trace, the footprint of the state" (robert henri)
"I do not always know what I want, but I do know what I don't want.” (stanley kubrick)
..by which I mean to say that you should just worry about making games for now. Then, when the game is done think about what you like and don't like about it and why. Then make the next game a little bit better.
The quote by robert henri pertains to shutting off your inner critic and "going with the flow" - if you are criticizing your own work while you are making it you will also be afraid to play around and experiment, which will prevent you from gaining fresh perspectives.
Don't consider what you're making as something which other people have to like - think of it as a toy which you're messing around with and try to remember what was fun and what wasn't. Then use that for your next project.
Don't think of making something as "putting the good bits in" but as "taking the bad bits away".
And as always the golden rule is to keep your nose to the grindstone - mastery takes practice.
Here's another old gem for ya: [url=http://www.twainquotes.com/Ideas.html]There is no such thing as a new idea.[/url] By extension, you're probably not going to make a unique game. Usually the best you can hope for is to put a new spin on an old idea and hope the combination works.
Usually when people say ideas are a dime a dozen, they mean just that: [i]ideas[/i] are a dime a dozen. Hell, you can have any number of good ideas just sitting on the shitter for a good push. Where the value comes from is the execution of the idea, to turn it into a concrete product. An idea realized can be worth quite a bit; an idea on its own is worth about as much as the toilet paper you use to wipe after your brainstorming session.