Your job is to sell me on you.
Before you can possibly convince me as the interviewer that you are right for the job, you have to believe it yourself. It's amazing how many candidates seem tentative and reluctant to express confidence in their own abilities. Remember, you are all alone once the interview starts. No one will sell you if you don't sell yourself. How can I believe in you if you don't believe in you? I am not here to sell you on our company until after you sell me. Once you have sold me on you, I will sell you on the position and the company, but not until then. So don't expect the interviewer to tell you why you are right for the job. That is your job.