Yeah, yeah. Hughes is my favorite character and everyone knows it, but my first favorite, before the stupid happyspy grabbed my brain and refused to let go, was Ed. Why? It's hard to remember it now, but once upon a time, he was pretty damn cool.
FMA is about growing up, about shedding the unrealistic view of a perfect world for that of flawed reality and being able to appreciate it all the same, so it's only fitting that the hero have some issues when it comes to growing up. He's emotionally frozen at about twelve years old, because to grow beyond that he'd have to face Issues. (Technically, late in the series he does grow up and face his Issues blah blah blah, but they really could have done it better. I'll be taking him from before then, anyway.) He'd have to admit that he did something wrong in transmuting his mother.
thenowhere is right, by the way; he's roughly as sexual as a toaster. He's a teenage boy, but he wards off such harbingers of adulthood as sexuality with his driving push towards his goals. I don't think he's entirely asexual (simply because it doesn't ring quite right to me), just too driven to let it stop him. Occasionally he'll get confused and big-eyed at a scantily-clad woman, but most of the time it doesn't even cross his mind.
He is a geek. Full of book smarts but stupid in most common-sense ways, utterly obsessive when he gets going, somewhat inept socially, and way too hot for books--yeah, it all adds up. It's one of his more endearing traits, to me, the fact that he has a hero's broken nobility and a geek's silliness.
He also has a child's insecurity. He knows better than to be afraid of the dark, but he's merely traded that fear in for slightly more complex ones about his own inadequacy. He wants his mommy. He wants--indeed, if anyone in the show is his dark shadow, it's Envy, the ultimate spoiled brat.
At his core is a complex combination of anger and loyalty. Anger, because he gave up so much and got nothing in return, and he doesn't understand why. He thought the world worked by Equivalent Trade. How is this fair? He could just admit that life isn't fair and move on--except he can't. He can't let go that easily, because if that's true, it was all for nothing. It means things can't be fixed. So instead he tries to force equivalent trade on the world, on the vague principle that maybe someday it'll get through.
Loyalty, because his brother is the sane core at the center of his crazy life. His relationship with Al is far from perfect. There was an episode or two where I whistled and went, 'Damn, that's practically an abusive relationship sometimes.' The way he takes Al for granted--that's not healthy at all, and he's going to need to change that. To do so, he'll have to grow up--and ultimately that may be his impetus for doing so, if he ever manages it. Because for all that he mistreats Al sometimes, he wants to make it all better more than anything in the world.
La la la, there's more to say than that, but it's early and I got very little sleep. Just know that there's more to the character than how tainted he's been.