Tolkien changed the story in the second edition to reflect the corruptive powers of the ring taking shape in "The Lord of the Rings" trilogy. In the original 1937 edition of "The Hobbit" Gollum was genuinely willing to bet his ring on the riddle game. The deal was that Bilbo would receive a "present" if he won. Gollum was disappointed when he couldn't keep his promise, because the ring was missing. He showed Bilbo the way out as an alternative, and they parted courteously.
As the writing of Lord of the Rings continued; the nature of the Ring changed. No longer a convenient magical object, it had become an irresistible power object, and Gollum's behavior now seemed inexplicable. Tolkien resolved the difficulty by re-writing the chapter into its present form, in which Gollum had no intention of giving up the Ring, but rather would show Bilbo the way out if he lost. Also, Gollum was made far more wretched, as befitted one enslaved and tormented by the Ruling Ring.