Justin. From the original Grandia.
Not only is Justin happy and optimistic, both of which I appreciate very much in a JRPG hero (I got FED UP with the "Moody Douchebag" - type of hero about 15 minutes into Final Fantasy VIII), he also possesses a unique quality the likes of which I have never seen in any other game of this type:
Justin is a perfectly ordinary person.
This is a very refreshing difference from the normal setup, where the hero is the ONLY person in the world that can keep the villain from destroying it.
Other RPG heroes need to travel the world to find out how to defeat the villain, or to collect the artifacts they need in order to do so. At the outset, Justin doesn't NEED to go anywhere. He DECIDES to travel the world, because he wants to explore it. He's just having fun. (He does end up saving the world anyway, but pretty much only by chance.)
This is MY motivation. This is why I play the game. I want to explore the game world. I want to have fun.
In other RPGs, I occasionally have trouble following the story because the heroes will stand around discussing plot details while I'm more eager to go and find out what's behind that mountain in the background. In Grandia, if there is a mountain on-screen, it's a safe bet that Justin feels the same way about it as I do.
It really is surprising how much difference something like that can make!