|Mary Sue cartoons property of MissLunaRose at deviantart.com|
Readers love to fall in love with your characters. If a character is created interestingly enough, they love to love them, and they love to hate them. I think it's a tremendous compliment to an author when the reader puts the book down, saying something unintelligible through gritted teeth ("arrrrrggggghhhh" will do nicely) because the character is so complex that they relate to them. They get angry with/at them, and can't forget them just because the book is closed.
You do, however, want to avoid having your readers hate the character because they simply hate how you've created him. Creating the perfect character doesn't necessarily mean that the character should BE perfect. In fact, that kind of thinking will backfire in a big, big way more often than not.
Think of real life: the "perfect" man or woman . . . we think of someone who always says yes to us, or fulfills our every desire, acquiescing to our whims. But in reality, someone like that would bore us because he has no spine, no personality, no chutzpah at all—which translates into bland, no give and take, and nothing adventurous to explore and discover. There is no challenge for growth or new ideas when someone is always in agreement with you.
Some of my favorite YouTube videos come from Terrible Writing Advice, and this one about "Mary Sue" (aka The Perfect Character) is a hoot:
Be cautious of the pitfalls of creating a character too perfect/cliché. Your readers will cease being your readers after a while. Characters become caricatures, and your reader will not only be pulled out of the story again and again by things like, What? Perfect grades, chiseled abs, AND he feeds the homeless and is the football captain, too?
When our kids were little, we used to read to them all the time (big surprise there). Most children can comprehend at a higher age level than their own reading level—they may be reading Little House in the Big Woods on their own but are able to completely understand The Hobbit when it's read aloud to them. So when our boys were six and eight, I think, we were reading the Hardy Boys books to them. The first book thrilled them. The second book was great. The third, not so much, and by the fourth book, the shine had completely worn off. Even at their young ages, our kids wondered why the boys were never in school or had jobs but had an endless supply of money and gas for their motorcycles. They always had the exact skills needed ("Frank, an amateur gymnast, was able to flip back and upward onto the water wheel at the mill . . ."), and the last straw for them was when the brothers needed to pick up some broken glass as evidence, and Frank just so happened to have a folded piece of cheesecloth in his wallet. I'll never forget our oldest saying, "Really? Cheesecloth? Who carries cheesecloth with them anywhere?"
Lesson to be learned: if your character has no flaws, your reader will begin to despise the very character you want them to love and connect with.