Can't they be happy you passed?
If your parents make you feel that bad over something as silly as valedictorian then... that's pretty messed up. People who get valedictorian really don't get anything big. I got it, I'm going to a college 3 states away soon, and I'm still going to be in debt. Valedictorian doesn't really help with anything, and yeah, my parents had that look, but you know, it really didn't matter to them, they were just happy that I passed and got into college because they knew that's what I wanted. : }
Not to be mean or rude to you or anything, but you really shouldn't worry about it - it's kinda silly to think you're not good enough over something like this. What matters in the end is what you did overall with your life.