At the end of the day, the Doctor is defined by one trait. His love for and faith in the human race. He's proven that he's willing to tear armies and worlds apart to save the people he cares about. He insists that in thousands of years of time travel, he's never met someone who doesn't matter. Not even the most moral person can claim to have always had this unshaken faith in humanity. And isn't an undying loyalty to one's friends the most admirable trait someone can have? That is undoubtedly the coolest thing about the Doctor. You may not be able to have a time travel machine, or a reputation that sends your adversaries running for their lives, but you can emulate this great commitment to your friends. After all, great friends are cool.
