The actor reprises the part of Gollum, having played the iconic motion-capture character in the second and third of Peter Jackson's Lord of the Rings films.
"He's such an amazing character, so varied, and Tolkien imbued him with such a lot of love," Serkis said. "I'm convinced that he really invested a lot of himself in that character.
"And then our writers, Philippa Boyens and Fran Walsh, just took it to another level for the movies, and really kind of examined and mined the split personality of Gollum and Sméagol for our version."
Serkis went on to discuss how much the technology has advanced since his experience on Lord of the Rings, and the extended one-on-one scene he shares with Martin Freeman as Bilbo.
He also commented on the much-discussed decision to turn two films into three.
"People think, 'Oh, well how can The Hobbit, which is one book, become three films?' But you can take one line from an appendice and it turns into a whole sequence.'
> 'The Hobbit: An Unexpected Journey' review
> Peter Jackson on 'The Hobbit' and 'Lord of the Rings' - video
The Hobbit: An Unexpected Journey is out now.
Watch Digital Spy speaking to Martin Freeman about The Hobbit below: