Warning - Contains Spoilers
FMA brotherhood has an incredible plotline. It's unpredictable, interesting, and incredibly original. There really isn't much I can say about the story that hasn't been said at some point, but straight up, this show completly deserves the praise it gets. I can also truly respect that they relaunched the anime and followed the manga, as opposed to it's predecessor. On a side note, all of my roommates have the brotherhood emblem tatted on them, with the exception of myself. If that doesnt give you an idea of how great the show is, than I don't know what does. I can't even think of anything else to say about the story line, it's seriously just that good.
So the animation isn't excellent, but it's still very good. The action scenes are done exceptionally well, and there is a lot of great scenery offered as well. Overall they did a solid job on animating and character designs.
Even though this show did have a solid soundtrack, there are still others with better ones. What the soundtrack did do exceptionally well though was use the music to portray emotions, a feat few animes can brag about.
Im still debating what the best part of the show; is the characters or the storyline. You wanna know how I know this is the best set of characters in any anime period? I actually sat down, and made a top 25 list of my favorite charcters for this site; and FMA brotherhood accounted for more than a third of the charcters on that list. And I didn't even include Ed or Al. Armstrong, armstrongs sister, ed, al, Scar, Mustang, Hawkeye... the list goes on and on. Even the bad guys are cool. Pride is badass, and so is Wrath. Greeds cool. The only other show I can even think of that has such an array of excellent characters is Game of Thrones. And that's not animated so I won't compare the two.
Overall, this isn't my personal favorite anime (top 5 though), but I can completly understand why it holds the #1 spot for animes. It completly epitomizes what a great show should have in it. I can't even think of anything bad to say about it.... man I really need to get better at writing reviews. At least I can leave you with the funniest scene of the series...