Definitely my preferred anime adaptation of the two. (massive spoilers)
Yes, yes, I know it's not true to the manga, but the thing about moving picture media is that it's all about presentation. Let me take a moment out of explaining that to say this: the manga is my favorite incarnation of Fullmetal Alchemist, above either anime. Now then...
2003 Anime:
When I say presentation, I mean a lot of things: initial reveal, design, development, clarity, and logos, ethos, and pathos. The 2003 anime didn't just throw us in to the thick of things at breakneck speed like it expected everyone to already have read the manga. Any decent adaptation is made with the expectation that they are drawing a new crowd as well as people who loved the original it came from and act accoridngly by properly introducing the characters and world. Then it will properly develop them and show us how it all works.
Episodes 1&2 of the series, we're introduced to Rose, a rather obvious audience stand-in who serves her purpose perfectly. Through the eyes of this simple girl living in a simple desert town, we watch this particular chapter of Elric brothers' story unfold. With her, we learn the principles and power of alchemy, about the Elrics and their motives, of the mystery surrounding the Philosopher's Stone with her, and of the good and bad that comes with alchemy depending on who uses it and why. We see what we need to see at that early stage and we're told the rest in very concise terms.
Then over the next 23 episode, we're told the backstory and present circumstances of Elrics proper, growing to know, empathize, and love them along the way. We also get to know and love many of the people around them. Mustang, Hawkeye, Hughes, Nina, Winry, Grandma, and more. These characters had so many sides to them, their strong points, their flaws, their motives, their aspirations, and their fears, and they were so nicely nuanced.
The story isn't rushed or dragged out. The first half of the series is near perfect apart from a couple of unnecessary filler. It's given time to breathe and we're allowed to familiarize ourselves with the world and its denizons.
Now, as for the second half of the series, I'm not going to deny it. It is somewhat problematic, but it isn't bad. I love how Dante is like a warped shadow counterpart of Ed showing just how wrong a person can go for selfish and petty reasons. Unlike Ed, she never learned her lessons about playing with fire.
Besides, I can't really blame the people who made the series. They were required to come up with their own ending, and for what they had to work with at the time, the creators did a very good job. I watched this through and finished the anime before I ever had a chance to read the manga, and I'm glad. It allowed me to just appreciate what I had in front of me without outside expectations. As a story in it's own right, it's fine. It's not perfect by any means, but what ever is. Even if the second half is weaker than the first, that's alright. We still had a solid story and a cast of characters we loved.
So in conclusion: Fantastic first half; just good second half. Overall, great show. It was funny, it was tragic, and it followed through with its themes: once you've lost something, you are NOT getting it back.
The movie sucked, though. Won't deny that.
Brotherhood:
I wish I could have enjoyed Brotherhood as much. The episodes that cover the manga are excellent. They're everything I could have ever hoped they'd be. Too bad I couldn't care less.
What? Yes, you heard me right. I have a bone to pick with the first 12-13 episodes of Brotherhood, which just ruin the whole thing for me. They cover the same ground as episodes 1-25 of the 2003 anime. Brotherhood had the opportunity to go back to the start and begin anew. To retell FMA more accurately to the manga, which they did in the long run, but...
They screwed up in the opening act by rushing it. I can understand that the showrunners being reluctant to have to retell the bits of the story that they poured so much heart into the first time around, but too bad. When you're telling a story, you HAVE to do it right. You have to take the time to get your audience into your world. You HAVE to properly develop all your characters and the story at a pace that can breathe. Brotherhood didn't do that.
Episode 1 is utterly useless.
Episode 2 is a poor man's retelling of the Father Cornello mini-arc.
Don't even get me started on how they handled the Tuckers in Brotherhood.
They obviously knew while working on the first anime that viewers needed to get to know Nina and her father in order for the inevitable to have the desired impact (our tears). So, they let the Tuckers hang around for a few episodes and then dedicated the whole of "Night of the Chimera's Cry" to them. Then in the following episode, they used the grisly fallout to showcase how each Elric handles loss (post-failed resurrection) and introduced us to Barry early.
In Brotherhood, we got Nina for one episode, and honestly, the whole ordeal was unintentional comedy at its finest. The big reveal at the end, it was so over the top that I actually burst out laughing. Laughing. At a little girl becoming her daddy's grisly science experiment. The dutch angles, the exaggerated faces and reactions, the music, everything just screamed of "trying too hard".
2003 anime: when the Elrics confront Shou Tucker, the scene took its time to build up and let the reveal come out naturally. It knew when to pause, but more importantly, it was restrained, like a dam building pressure. The dam finally breaks when Ed completely loses it and beats Tucker half to death with his automail arm. The music was somber and lowbeat, the expressions and reactions were more subdued, the angles were simple and they just let the scene tell itself. Then, when all is said and done and Scar enters the scene, the viewer is left just as shocked and horrorstruck as Ed and Al.
In Brotherhood, it's more "Well, that's sad." Yeah, it is, but it's not the soul-crushing climax of the original.
And then there's the big one: Hughes. In the 2003 anime, we get to know Hughes through the first season very, very well. His personality, his kindness, his quirks, his hopes, his dreams, his family, and his friends. He's easily one of the most likeable characters of the whole show. So, obviously, when he went the way of Nina, there were more bitter tears to be had. Much like Nina, the final hours of his life got an entire episode dedicated to them and the impact of his death was played perfectly with a cold closing.
We barely get to know Hughes in Brotherhood and his death, while still sad, is once again, just not the soul-crushing finish the first anime had.
This right here is the linchpin for why I couldn't get into Brotherhood. It doesn't matter if the episodes after the first act accurately retell the manga. In fact, I would dare say that the episodes 14-64 of Brotherhood are a heck of a lot better than episodes 26-51 of the 2003 anime. I still like the 2003 one better because it put so much loving effort into giving me reasons to become invested in what happened to the Elrics and the world around them.
Brotherhood treated the early chapters like an obstacle to be overcome rather than a story to be told. It couldn't be bothered to make me care like the first one did. Brotherhood just assumed that I knew the world and characters and just never bothered developing them until after it actually started having a coherent narrative around episode 13-14.
It's a shame, too, because there is a lot in the early chapters covered by the 2003 anime that never made it into either adaptation. I will say one thing for Brotherhood, though, though: it had a much more likeable Roy Mustang from the beginning. Mustang in the 2003 series just rubbed me the wrong way. I only really started to like him in the final episodes of that series. He's much more accessible as a character in the manga and in Brotherhood.
This is all just my opinion, though. I hope you didn't find this rant too boring.
"All you have to decide is what to do with the time that is given to you." -Gandalf