FF9
Because it wraps up every single little in the game, is very inspiring, full of great music and uses that same circumstances as the intro to show the contrast between how the world and the characters were before, and how they are after.
And it is half an hour long from the moment you slay the endboss.
For some reason, I'm okay with the length, because for a 50 hour game, 1/2 hour for a incredibly fulfilling ending is simply sublime. Because ending a 20 hour game with a two minute sequnce (Bioshock) makes me feel kinda empty, but this end just fills me up with hope and strength (Disclaimer: love both games, just comparing the emotions i feel from their endings)