To be honest, at first I was disapointed when I was told that Leona Lewis would be doing the theme track because I don't want to listen to some beyonce wannabe while I'm playing final fantasy. ThenI had a realisation that the usual team would be composing the music and she would just be doing the vocals which wouldn't be so bad, only to be then slapped in the face by the video saying they are taking the song straight of her new album.
As far as her winning X-factor as a judge of skill, so did 4 other people who we never here about any more (and in my own oppinion, Ben Mills was better by a long shot), not to mention this year which I haven't watched, but I've heard enough about Jedward the twins to know that even though they can't sing, they go through every week.
The botom line is Leona is a pop person which is a marmite genre of music, whereas the melodic traditional music of the FF series has appealed to just about everyone who plays it (lets face the facts, it's a hell of a long game to play to music you don't like).
SE may not be able to get out of a contract with Lewis' record company, but surely they can put in an option to use the planned Sound track, or use the Japanese sound track for those who don't.