It's one of the greatest even though it deviates (rather purposefully and with the creator's blessing) from its manga origins. I haven't read the manga. I will, but right now I don't know much about the manga and at just what point this anime deviates from the manga. I won't comment exactly what the differences are until I make my way through the manga. I just know that, from what little I've allowed myself to read on the subject, this anime and the manga aren't exactly twins after a certain point. Almost from the start I think there are deviations, but if I really wanted to hazard a concrete guess I'd say this anime becomes completely original material at the halfway mark.

Also, to help avoid any confusion, this series was remade completely and given the title of
Fullmetal Alchemist: Brotherhood. That title is said to follow the manga a lot closer. They are not the same series or related to each other in sequel/prequel fashion. While I am at it, I should state that the movie
Conqueror of Shamballa is a movie sequel to the first anime series while the movie
The Sacred Star of Milos is part of the remake series. Haven't seen either of those movies or the remake series, but I figure a quick disclaimer explaining the differences between the two series will keep people from saying, "Hey, man, that show wasn't anything like you described. Your mother was a hamster and your father smells of elderberries!"
The anime is an experience and it requires a bit of attention while watching. A lot of anime you can watch while zoning out, but this isn't really one of them. The story is in the dialog and there are a lot of characters changing places. If you aren't paying attention you'll think, "Wait a minute, I thought that guy was at Central, but now he is in the East? Wait a minute, now he is in Central again? What the hell is going on?"
There's action and fights, but not a ton of them. There's also some comedy and during the early episodes it works pretty well, but toward the end it feels a bit out of place as the storyline gets more and more serious. When it is working at its best
Fullmetal Alchemist is a drama about the human condition. At its worst it is a bit too repetitive on the more sentimental aspects of the show. It also gets a bit too deep for almost no reason at times. The story is purposefully cryptic and tough to really digest on the first time around so I'm sure there are things I missed or didn't catch, but I almost felt the atmosphere was a little too cryptic. I'll get to that later, though.
Every episode talks about the Philosopher's Stone and what it takes to create it. Is it the Law of Equivalent Exchange or is it something else? How do you make it? These are the questions that push the series and the Elric brothers through their journey.
What sent them on the journey to start with? Well, it all started with the death of their mother. Edward and Alphonse were so stricken with grief that they tried to bring their mother back using alchemy. Unfortunately it backfired so badly that both Edward and Alphonse were scarred for life and their mother still remained dead.

Ed lost his right arm and left leg and Al lost his entire body. Al is now trapped in a feelingless suit of armor while Ed's limbs have been replaced with automail. Desperate to get their bodies back to normal, the two young alchemists search out how to make the Philosopher's Stone. However, to do so Ed must become a "dog of the military" if he wants to get closer to the truth and gain access to classified materials.
As a State Alchemist working for the military, Edward Elric is dubbed the "Fullmetal Alchemist" and journeys in search of the Philosopher's Stone with his brother (who really is the fullmetal one because of his body) during his free time.
However, there are plenty of others looking for the Philosopher's Stone and not all of them are nice or human.
There's a guy with a scar on his face going around killing State Alchemists, there's seven bad guys running around that can't seem to die, and even a guy willing to sacrifice his own daughter in order to make the perfect chimera.
There are good guys, but it is tough to understand who they are because as the anime continues everyone seems to switch sides a dozen times. Another reason why the dialog is really important.
The first half of the series is heavy on the flashbacks. This series actually starts in medias res and then goes back to the start on episode 3 and this flashback occurs continuously until episode 9. By the time episode 10 comes around you'll finally be moving forward with the story and pretty much familiar with everything I just described above.

The second half of the series is where things get really crazy and the final few episodes create one of the odder and more abstract endings I've seen since
Neon Genesis Evangelion. Sometimes things get too crazy with all of the characters switching sides or giving help to characters you wouldn't think they'd help, but I suppose it is a credit to this anime and its writers that it's impossible to know what is going to happen next.
I did not see that ending coming at all. I know the lady who wrote the manga helped out on the anime, but I believe that the ending (as well as just about everything else) of this anime is purposefully unrecognizable when compared to the manga and that of
Fullmetal Alchemist: Brotherhood. So I've got some great characters to revisit soon. I can't wait.
Anyway, let's dish out some goods.
The one guy everyone seems to hate is Shou Tucker and it is with pretty good reason that you should hate him. You'll hate him even more once you realize that he's a character that will stick around throughout most of the anime series. He's not even the main bad guy or anything like that, but he probably does one of the most despicable acts of all the villains in this series. He does something even worse than Pride strangling his child. Although that was pretty damn bad, too. Fuck you, Shou Tucker and Pride. Ya'll both suck.
Scar is a fascinating character and I think he has the most depth of any of the characters, next to maybe Lust. Of course, the primary attraction are the characters of Edward and Alphonse and they are more than enough to carry this anime forward, but there are plenty other characters around them that feel like more than drawings on a page.
Maes Hughes is one of those special characters, though. If you want a strictly anime comparison then I'd say he's a more family-friendly version of Jiraiya from
Naruto. Hughes has something in common with that character I just mentioned, too. His character is that of a father figure and that's something Ed and Al always lacked because their father ran away on them when they were young. Since the two of them have arrived in the military Hughes seemed like their pillar of strength. He's also pretty funny. As much as they hated Mustang they loved Hughes. Specifically, Edward. So it is thanks to Hughes and those bastard Homunculi creatures that we have what is probably the saddest moment in the anime. Those tissues, folks. Bring them.
Greed was a really cool character that got killed off way too soon. He was only around a few episodes.
Roy Mustang was a cool character, but it seemed like he was nonexistent throughout the anime when he wasn't being the center of attention. He was literally either there and kicking ass or not there at all and almost an afterthought. With his past in Ishbal it seemed like he could easily have become one of the central characters, but he never really felt like one of those to me. He is definitely an important character and he gets to do some really cool things, but I felt that he could have done so much more earlier on if he had been given more information.
Of course, that's one thing that got on my nerves as the series progressed. No one in this series communicated with each other. At all. This series take place in alternate universe in some 1900's European landscape where most people take a train to go somewhere. So that could be a contributing reason why no one talks to each other, but it feels to me that the writers forced that issue a bit too much at times. Even Armstrong, who seemed like he was attached to the back pocket of the Elric brothers at one point, seemed to stop communicating with everyone including Mustang for a time.
Armstrong is another awesome character, by the way.
With no one talking to each other it seemed almost too easy for the bad guys to get so deep inside of the military. It's like one of the writers said, "If everyone is all close and stuff like Hughes then this story will end in no time. So let's just shut everyone up for a while and send them on wild goose chases." That's what I meant earlier when I said things were a bit too cryptic at times.
This could still be an issue in the manga and the remake anime, but in this anime it feels like it was just pushed a bit too much to me by the writers. Edward doesn't even find out about the death of Hughes (episode 25) until episode 44. Hughes ironically died for not telling Mustang about his findings. Guess no one learned anything from that.
That isn't really a knock on this series, though. I was moved enough by it to be little more critical then maybe I should be. The folks responsible for this anime toyed with my emotions and my expectations. I just wished that everyone could have just talked this stuff out without a bunch of people getting killed.
I would highly recommend this anime to anyone. It really is one of the classics. Although I do have a few reservations about how the second half was handled you won't find many much better.