Ok so you've heard the phrase "Rome wasn't built in a day." Well the fact is that very few things are built in a day and even fewer things are built well. Many times when I talk to people about their projects, software or designs there is an expectation that the ultimate design, software or product could be just around the corner. Or in most cases just around a version away. The truth is that design isn't perfect and the way to build great products is to evolve them from small building blocks. Build in the expectations that each version is a progression to the next version. Take baby steps and take them often.
Start with an idea, a nugget, a meme and start working on it. There may be similar ideas out there but none quite like yours. Don't be discouraged that your idea doesn't have all the features that the other ideas have. Focus on the differences. Good designs are built like building blocks, often in little phases. Each block can be sculpted to look great. Then the pieces are put together and the whole thing begins to take shape. Design and product evolution take time.
A friend of mine had an idea for a product that helps you sell shareware, "But there are already products that do this, so I'm not going to bother." Of course there are products that already do this. Ideas and products evolve from each other. Most good ideas occur in multiple forms at the same time. The car was invented by 5-6 different groups all around the same time, similarly with the airplane, telephone and others.
Stop sitting on your ideas and start building the blocks that can make the idea happen.