Before Geralt, it was Auron...he died a young age for no reason whatsoever besides being an upstart kid. He then accepts his fate (like a boss) and is given a second chance to save the world. He then comes back later to help Sora in KH2....I know his badass line is "this is your story"....but it seems like Auron is the main character in anything he's in, for good reason.
Geralt takes it of course, mainly due to the fact that he never had any intention of being a Witcher, yet he decided to help the world anyway. He couldn't have kids, and fate rewarded his efforts with Ciri, he was considered a monster, so the gods blessed him with chivalry. The life of a Witcher is a lonely one, nothing about it is glamorous. You get spat on for the myth/rumors of eating babies and being "demons", and everyone thinks you'll jump for any amount of coin. Geralt chose to be a righteous man in the form of a Witcher, and that is a hell all on its own.