In an odd turn of events, the last three games I have played have involved Time Travel in one way or another. Nine Hours, Nine Persons, Nine Doors requires the player to replay the game using knowledge they have acquired from past playthroughs in order to uncover the truth behind the situation the characters are trapped in. Ghost Trick: Phantom Detective has the player watch the events leading up to a characters' death in order to figure out how to stop it. Finally, Radiant Historia has the main character jumping through multiple timelines, trying to uncover the "real" history by obtaining knowledge in one timeline, then using it to his advantage in the other.
While these three games have been actively calling attention to the fact that the player is using knowledge of the future in order to change it, this is hardly a new phenomenon in games. We've all played a game where a particular level was difficult, and managed to bypass it not through skill or cunning, but by memorizing where the enemies would be and when the traps would activate. We've reloaded a save file in Heavy Rain in order to undo a mistake we made. Anybody who has played Serious Sam knows that the game is nearly impossible without constant use of the quicksave button.
However, the use of saving and reloading in order to play at your best has a tendency to break the immersion. Sometimes we get wrapped up in going for the optimal ending, or the highest score in a level, that the game ceases to be fun. We willingly hurt our enjoyment of the game in order to play it the "right" way, even if the game designer never intended it. Games with multiple endings tend to be the worst offenders of this. After all, we have seen most of the game anyway, and there's nothing worse than slogging through the old content just to see more of the game. That's why deleted scenes on DVDs are separate from the main movie. We've already seen the majority of the film, so we would rather just skip straight to the cut content, because that's what is new.
Radiant Historia gives us a unique way to handle this problem. Rather than requiring the player to play through the game every time a choice must be made, the game gives you several "nodes" to travel to whenever you have the chance. Critical decisions that will have an effect on the timeline are pointed out, and there is a map that shows you where the choices diverge. A lot of the time, the "choices" only amount to what is essentially a nonstandard game over screen, but these serve a purpose. Oftentimes, the choices we make in game stories are at the discretion of the writer, not the player, and we sometimes wish we could see how things could go differently.
From a design standpoint, the alternate choices in Radiant Historia are frustrating. Why give the player a choice when one of the options leads to a bad ending? It reminds me of the choices in King's Quest, which were frustrating because they only served to waste the player's time. But from a writing perspective, these alternate paths in Radiant Historia at least serve to explain to the player why the story is going where it is. Whenever a wrong path is chosen, the player is given a summary of the consequences of his decision, and how it will diverge from the "true" story.
It can be debated whether or not Radiant Historia uses time travel as a gameplay mechanic or a plot device, but either way it's an interesting take on game storytelling. We definitely can't tell a story like that in a movie, and choose-your-own-adventure books are its closest literary comparison (which really aren't taken seriously as far as writing is concerned). It's an interesting mechanic that really enhances an otherwise run of the mill JRPG.