Monsters of the Id (movie, 2007)

Nathan becomes a super hero style of character in people's dreams to rescue them from their nightmares, only to realize he's not the only one. Not only that, but he has been manipulated to become one by them in order to help these good guys defeat a new foe, the Nemesis. Nathan is reluctant at first but comes around to figure out exactly where the Nemesis is coming from, and why, and how they might be able to stop it.