It's almost impossible to find design that is 100% unique in this day, and age. Art Style, Good Design, and more important than all of that is the fun factor. If the game is fun, that's all you really need. Of course, the former certainly lend their hand to the latter. But game design should never be focused in making it as "Unique" as possible, but as intuitive, and fun as possible. If that's a philosophy that is echoed a lot, than maybe there is a science to that.

5 minutes ago, Vidionix said:

Thanks! I feel like it will be immediately labeled as a Sonic ripoff and nothing more.

What's wrong with being a Sonic Ripoff? The early Sonic games kicked butt. Unless you're ripping off the new ones O_o Take what they did in Sonic, and improve on it. Taking in what they did, distilling it, see why it worked, and do it better. Greatness is usually achieved by standing on the shoulders of those who came before you.

In addition to markypooch's good advice, I would recommend looking at what is fun about your game rather than how it is similar to others. To do that just look at what makes a game fun in the first place: meaningful progress. In Sonic this was accomplished by collecting rings and learning mechanics that improved your ability to move forward and the speed at which you did so. How will your game convey meaningful progress?