So...it's mostly between Roxas and Riku, huh?
Well then I guess I'll go for the underdog and pick...Sora. Afterall, to actually see his character one does have to look a bit more deeply over the course of multiple games, instead of the blatant spoon fed emo angsting.
Sora is an optimist so he tends to bottle up his negative emotions and feelings and really tries to hide that sad side of himself for his friends(Donald and Goofy, among others), so it's just different. Most people overlook his character because he's main, but it's there, nonetheless. Though I do really like Roxas and Riku.