Most FF fans in America have terrible tastes, tbqh. I played all of those games and objectively speaking, only Aerith had a more shocking and devastating death. The fact it looks like you won and then it turns out Galuf is permanently dead is a massive gut punch that turns the plot way more personal than Tellah's 'I MUST AVENGE!!' or Vivi's death-by-omission in FF9's ending. Tidus' death is arguable, sure, but even in FFX itself it's heavily implied he actually reincarnated so it doesn't have the same kind of impact as a true final death. You can even see it in how the rest of the world reacts to it. Where's the reaction to Tellah's passing, compared to Galuf's? His friends mourn him, Gilgamesh gets very quiet when he finds out the old geezer is gone, and in general, it's a lot more 'real' than the other instances, bar again Aerith who did much the same thing but even harsher.