The FFT ending is quite possibly my favorite ending of any game/movie/book. I remember the first time I beat it I just sat there for a few minutes in stunned silence thinking ''wow, I can't believe they did that'. It is open enough for you to believe that they lived or died. I like endings that leave it open enough to wonder, but keep the choices to two or three outcomes so that each is well developed and plausable. (I feel the ending where they all die is the far superior one). Having everyone live happily ever after would just ruin the entire tone of the game up until that point.

Likewise we have another big question with the whole Delitia/Ovelia situation. Though many people see this as a confirmation that Delitia has become a 'bad guy' I see it in a far different manner. Delitia and Ramza are both heroes, and the game shows just what you get for being a hero.
Ramza saved Ivalice from Lucavi, and in turn was ostracized from society and ultimately ended up dying in a selfless struggle to save the world.
Delitia ultimately sold his soul to become king and be in a position to save Ivalice from itself, and in return lost himself and anyone he could ever call a loved one/friend. He saved Ivalice but ultimately lost everything himself.
Both are tragic heroes in my eyes, which is what makes the story so powerful.