Zelda: Ocarina Of Time

https://www.youtube.com/watch?v=upksegfWJeY 

As one of the greatest series of all time, Zelda is a gaming titan, one that's graced every Nintendo platform since the NES. Arguably the best game in the series is the fantastic Ocarina Of Time, originally released for the Nintendo 64.
After the brilliant boss fight against Gannondorf, and eventually his monstrous form of Ganon, the sages seal Gannondorf away, and with Zelda now safe, she and Link bid farewell. Zelda sends adult Link back to his younger days, safe in the knowledge that, for now, the danger is over. After the credits, we see Link, now a child again, return to the Temple of Time, and Navi flies off into the sunlight. The credits end with bells ringing, as he camera pans over the Master Sword. Finally, young Link returns to the gardens to meet young Zelda.
The ending is good on it's own merits, but compared to some of the others here, not incredible. So, why is it number five? It deserves this place as this ending is actually where Nintendo officially split the Zelda timeline into three, and this changed the entire series, and helped to explain the crazy, convoluted timeline.
Three possible outcomes of the battle with Ganon were posed. In timeline A, known as the Adult Timeline, Link defeats Ganon, who is sealed in the Sacred Realm. Ganondorf escapes this seal, however, and causes a great flood. This leads to the Wind Waker timeline.
Timeline B, or the Child Timeline, sees Link preventing Ganon's acquisition of the Triforce, which he does after defeating Ganon and returning to his youthful years. Here he alters events, and changes the future. Ganondorf attacks Hyrule, but is defeated and banished to the Twilight Realm. Link leaves Hyrule, which leads to Majora's Mask, and in turn, Twilight Princess.
The final timeline, timeline C, sees Link fall to Ganondorf in the last battle of Ocarina of Time. With Link defeated, Ganondorf gains the Triforce, but is defeated by Zelda, and sealed away, along with the Triforce in the Sacred Realm. This realm soon becomes dark under Ganondorf's rule. This leads to the events of A Link to the Past.
The fact that a game series needs such setup to explain its many different instalments and their relation could be put down to bad planning (which is quite possibly was), but regardless, Zelda is a mammoth series with millions upon millions of fans and this is the ending that literally changed the game's world.