I actually read an article [http://www.thegia.com/2013/12/06/final-fantasy-x-2-life-is-such-a-changing-art/] recently that made quite a good justification for X-2's existence. The idea is that it's so much the opposite of X with everything from level-structure to combat system to story and characters that they actually reflect each other pretty well.
FFX is about a world floundering under the weight of a pain so ferocious that no civilisation can flourish and life is about constantly making sacrifices just to keep the status quo. It's about how people cope with that and what they value to get through their lives when they own so little. Their religion, their relationships with the people around them, their sport, their belief that this might be the last time.
FFX-2 is about what you do when the storm is gone, relearning to enjoy life and not have to take things so seriously. Instead of being the person who takes on everyone's burdens Yuna gets to focus on finding out who she is and do something selfish for once. She can run around with friends pretending to be heroes and enjoy music and reconciliation. It's about having a future and choosing what it's going to be.
...but this sounds horrible, like it would undo all that closure and symmetry (and make X-2 completely pointless). They should never bring Sin back
verdant monkai said:
FF X is my favourite instalment in the series. I haven't played FF X-2 yet as the wide spread condemnation has put me off. That and I dont want to play as Rikku.
X-2 isn't actually quite as bad as it sounds. It's problem is more about what people were expecting than about what it is, if you don't come into it with those expectations then it's actually pretty fun for what it is.
Fun is the important word. FFX is one of my favourite all time games, FFX-2 isn't, but it doesn't try to be either. It's meant to be a fun epilogue that you can play enjoy and forget*
*If you do ever play it and then like it enough that you want to play it again somehow (there's a lot of branching choices this time around), look up a game guide. Tidus' storyline only gets resolved if you read one and deliberately try to get it. It involves random button mashing in an unmarked place in two particular moments over the whole game