Warning: Maybe Some Spoilers?
Major props - for doing things I thought were impossible; aka ending this show properly, this is one of the shows that I thought would bring disappointment regardless of the ending, but was proved me wrong.
After about season two I was pretty much addicted to the crazy life of the Elric Brothers, literally staying up as much as my body would let me to watch the next episode. Something rationality told me to calm down years ago, this show had the power to make me relapse into.
The character development was phenomenal; I felt emotions for characters far beyond my expectations, emotions that caught me off guard.
The Plot - unpredictable, well unless you read the Manga, in comparison to the original FMA series, this show is far better.
FMA: Brotherhood is similar to the first use the most addictive substance you can fathom, you just crave more.