I'd say that the perception of Jean Valjean being a flat saint is mostly due in part to the musical *cough*bringhimhome*cough*. But even in the musical, Jean Valjean is a very interesting character. You see in the Prologue that he's hardened and bitter from 19 years in prison. Then that act of unexpected mercy from the Bishop of Digne turned his world upside down, we all know the story, right? Valjean's Soliloquy is a very dramatic song because it shows a change of character that happens in a very short time. Even though he makes his decision to try and live a good life, Valjean still struggles with temptation, just like all us. I mean, Who Am I anyone? This song is one of my favorites from the musical, and I love how at the beginning he's tossing around his options, but eventually realizes that he must do what is right. Of course, for the rest of the play, Jean Valjean's is pretty much French Santa Claus, being good and saintly.
It would have been interesting if Bring Him Home was more about Valjean begging God to give him the strength to do what's right, that way the audience could see him once more fight his way through temptation. In the book, Jean Valjean hated Marius even as he was carrying him through the sewers. It was very brave of him to do what he knew was right, even if he didn't particularly want to. But you know, Bring Him Home is pretty, so I guess that's okay too.
At the risk of sounding morbid, I'd just like to finish up here by saying that I like how the story ends with Jean Valjean's death. I know, it sounds weird, but hear me out. There are a ton of subplots, some bigger than others, but all serve the same purpose in the narrative, and that would be the furthering of Valjean's journey to eventual salvation. I think that the book (and musical) ending with Valjean's death makes for a lovely, complete, and ultimately satisfying end to his long struggle.
I think Jean Valjean is relatable, even though I'm not a sixty year old man who spent a heckuvalotta time in prison. He's relatable because he's a person who made some mistakes in the past, and is doing his best to overcome them. He's scrupulous, he's scared of giving into temptation. To some that might seem like self-righteousness, but c'mon. Self-Righteous is the last word I would use to describe Jean Valjean.
So! I guess that's it, I hope you enjoyed reading my gargantuan text bricks. :)