Three weeks ago, Roger Ebert answered a letter from a reader who wonders if the Gollum from the Lord of the Rings trilogy should get an Oscar nomination. I have not seen this trilogy, so I can't judge on the merits of acting first hand, but he's become a big enough character to bust out into the popular culture. (And honestly, who would have thought anything by Tolkien would become a popular culture phenomena?) However, Ebert brings up an interesting thought. Gollum is probably rendered better than any of the characters in Final Fantasy, but he looks less human. Unintuitively, that may have let people become more emotionally connected to him. If the Gollum looked like...say... Haley Joel Osment perhaps people would have been repulsed.
According to a New Yorker article by John Seabrook, "Mori tested people's emotional responses to a wide variety of robots, from non-humanoid to completely humanoid. He found that the human tendency to empathize with machines increases as the robot becomes more human. But at a certain point, when the robot becomes too human, the emotional sympathy abruptly ceases, and revulsion takes its place. People began to notice not the charmingly human characteristics of the robot but the creepy zombielike differences." A definition on the Word Spy Web site gives more examples.
Simply put, you can reach a point where you can make it easier to notice the minute flaws than the many likenesses.
If you had the compunction to visit the link under the name Haley Joel Osment, you noticed it went not to a bio of him on the IMDB, but to a review blurb from a Joanne Jacobs where I believe she (and Virginia Postrel by proxy of link approval) manages to miss the point of the movie A.I.. It was deliberate that Osment's expression of love and want would be creepy to the family. If it wasn't for that, when David (Osment's character in the film) went after mom with the scissors to cut a lock of her hair, the family wouldn't have decided to want to deactivate David. (The compromise of compassion of course was to just abandon David in the wood.) But David falls deliberately within what is called the Uncanny Valley. (Honestly, I've been wanting to refute Joanne Jacobs on this for the longest time. If anyone wants to send note of this to her, feel free to.)
Even though this theory was conceived in the realm of robotics and A.I., you can see it demonstrated elsewhere. For example, in animation, rotoscoping is the practice of tracing real life movement onto paper. In practice, a rotoscoped segment in an animated film looks less realistic and fluid than ones where the animators allowed their little exaggerations of movement and squashing and stretching to come through. Also with computer animation, when they were making Shrek the animators had to pull back on making Princess Fiorna look too realistic. Also, if you look at the chart from backwards, you can figure why there are rapidly diminishing returns when you airbrush a picture to removes blemishes in a attempt to improve it. You can easily make the picture look worse!
Or why no one will ever buy a </a></b></a>karlgrenzebot.