We love suffering. The conclusion to a story isn't satisfying if it wasn't hard to get there. If Harry Potter lived a charmed life, never dealt with loss, and easily learned every potion and spell, his defeat of Voldemort would have been a mediocre pleasure, if that. But as a picked-on orphan, who struggles with school, watches friends die, and carries a heavy burden, we really like Harry and want him to win.
A lack of suffering makes for a "Mary-Sue" character, one that is practically perfect in every way. I found this "Mary-Sue" online test that was interesting. Not sure how accurate it is since some of the questions are a little unusual, but it was fun to take, nevertheless. Go ahead, check it out:
http://www.ponylandpress.com/ms-test.html
I scored a 19 for the main character of the book I'm currently working on. How does the test rate your characters? How does it rate the characters you've read and loved? What are your favorite characters and why? Let's discuss!