Generally, alternative endings are considered to have no bearing on the canonical narrative.
In other cases, ideas that were presented but discarded early on are alluded to by the production team in commentary or interviews.
The following are examples of alternative endings to movies: In TV shows, producers may want to keep the ending of an episode a secret, even if it means keeping it from the stars themselves.
Since video games are an interactive medium, these endings are generally posed as a result of player action, such as completing the game in a harder difficulty, taking a different route through the game's storyline and succeeding or failing at given tasks.
It is generally possible to play a game a second time, make different decisions or achieve a different degree of success, and arrive at a different ending than the first time, complicating the canonicity of the ending(s).