Oh, honey. You're not a failure. Children will be children ... and I'm living proof that not all siblings are the same. I was ... um ... err ... like your son, and my sister was an angel. And my oldest daughter is the angel and my youngest is ... me.
Try looking at it from a different point of view: His outgoing behavior will be a positive thing when he get's older. He's a go getter. Chances are he will be a very successful adult. He challenges authority. He may be just the legislator our childrens' future needs!
He knows how to behave. He proves it every day at preschool. There. That's proof that you're doing something right. And, I'll bet he does respect you. He's just testing you - seeing where his boundaries are and just what it's going to take to make you react. And he's waiting for the second you react, because then, he's won.
Take a deep breath and ... well ... just love him. You're doing a great job, I'm sure. He's just a kid.
My best wishes.