There's a certain type of feeling you get, very subtle, when a talented author of a book or manga in this case has done a lot of thinking, planning, heavy research etc. It shows in the cracks of the character interaction, the moderation of the plot, the easy secure feel of the workings of the world. I stumbled onto FMA while boredly perusing reams of manga, and boredly read the first few chapters. I thought it was pretty sterotypical adventure manga at first, with a nicely effective art style (some shoujo I swear to god) and good pacing, so I bookmarked it, read a few more chapters and at some point realized I never stopped. The characters were charming, EVERY character, the comedic timing was always on the mark and not overused, the plot was serious and unpandering, and the story soon revealed an ambitious reach with a full on alternate history, war, and crazy genius foreshadowing. The thing about this series is the gritty realism it portrays without resorting to over-detailed art styles or being a backstreet fight manga. Even with the fantasy-esque alchemy it was integrated so naturally into the series, action, history, and personality of the characters that it just became an awesome personal trait kind of feel rather than a contrived plot device. (which it wasn't.)
Visual wise the fight scenes are dramatic and dynamic, the tragedy is emphatic and almost understated (but with lasting effects- such as trauma) and the drawing style is amazingly serviceable and distinct. Personally I loved it, but others may think differently because... I frankly have no idea. If an author can age up a character that subtly through 25 volumes they are very skilled in my book.
The best part of the series (besides the sneaky philosophy at the end) were the characters. The women characters were all amazing and individuals with lives beyond the lead for one, and the main character and his brother were great foils for eachother— the situation the homunculi put them through really made them grow up for better or worse. Off the top of my head, Riza, Mei, Ling, and Scar were hugely developed characters instead of being the two-dimensional throwoffs they could have been (in another series), instead making the plot so three dimensional it firmly cemented FMA as my top series.
This would be a good gateway series to introduce someone to the potential of the medium.