Why is this?
Unlike so many of the other doujinshi I read, FMA doujinshi is beautiful. (Key young TK voice...or rather, on second thought, do not). Do not misunderstand me, FMA has its exceptions. I have had occasion to glance upon artwork or page through stories that could rival the worst of any fandom.
But so very (and increasingly, it seems) often I am blown away by both the beauty in the artwork and the amazingly painful, if human, stories this fandom has spawned. I find myself enjoying the FMA doujinshi not for their relation to the manga, but rather as they stand by themselves.
As to the anime...
>^..^<      J. Washington Irving