Lightning shows signs of remorse about her sister as well as devotion to both duty and family, something Cloud eventually ends up being. The whole purpose of Lightning doing what she does is because of the love of her sister.

And Vanille is the narrator of the game. There is a clear juxtaposition in the immature oohing and aahing she does in-game to the sad, lonely narration that she provides. This would suggest something new to the character.

Hope starts off whiney and useless, but develops immensely throughout the game. His story-arc is one of the longest and most realistic of all the characters (accounting for this being a fantasy game and it mirroring a whole lot of coming of age stories).

Sazh - generic? Who exactly is he similar to? And Snow? And Fang? I made a thread about this. There seems to be a combination of characters in them, but not 1 unique character from any Final Fantasy.