I think that Gollum has human (er, hobbit) eyes to remain sympathetic, or else the pity shown him by Frodo in TTT would be less believable than it was. They make Gollum scary by his motives and actions, not by just his appearance.
Care to explain the reason? I assumed it was because of the literal fall he took at the end of TDK. Or is it some stupid smartass writing to show that Bruce must learn to live without the cane (Caine, Alfred).