One of the greatest compliments I've ever heard (and that I can think of) was given to my wife by a friend who is not a Christian.
When they first met and started hanging out she found out my wife was a Christian...she told her: "we won't be friends long." All she had experienced from Christians was judgment and condemnation so she had a right to be skeptical.
After they established a friendship for a few years this friend said to my wife: "if I ever do become a Christian, it will be because of you."
That's the kind of witness I hope I have for Jesus.