Maybe you should start working to better yourself and stop thinking that you are so much better than your sister. Sometimes when people compare themselves over and over to someone else, problems arise. It seems that you have a jealousy issue, obviously, and that doesn't make other people see the best in you... Do what makes you happy with yourself... Once you decide to be happy with who and how you are... And stop concerning yourself with how differently your sister gets treated... Your parents will see how strong willed, responsible, unique, intelligent, respectful and caring you truly are...
Well if what ur saying is true I might be able to help.
It's been said and proven true that parents have there favorite child, and it's true in my family, my brother is the favorite. And I fel unloved, I finally confronted my dad and told him how I felt and he realized it was true and saw it from my perspective and said he was sorry and said he wants to b a better father. And that was just today! But we'll see how it works out but it can't get worse.
But don't blame your sister becuase just like my brother couldn't help that he was the favorite and I never got praised for anything ever, same for you sister can't help what your parets do and don't do. So just confront your parents and let them know how you feel.
There could be a dynamic that you are not aware of in your family. Talk to your parents about it. I know that sometimes parents will see one of their children, who they love very much, struggle. Imagine if your sister feels like you are superior to her. Imagine how much that would hurt. She would need a lot of encouragement and love because she constantly sees you achieve. Your parents probably recognize that and give her that extra praise and encouragement. Also, it is not for you to judge what merits praise from your parents.