So how did you guys like the ending of the manga, and the series overall?
I found it interesting how in the end the author made it so... symbolic. From how I'm understanding the story and the author, Greed gave up his desire for power (and his life) for the sake of his deepest desire, friendship, and Ed gave up ultimate "truth"/knowledge for the sake of his loved ones. The main villain was seeking ultimate knowledge/power the whole time, which is why he attempted to absorb god/become a god, more than human, more than a homunculus. But in the end it was his undoing.
It was said by "truth" that homunculus should've been satisfied with the nature of his existence, inside that flask. It also said, in summary, the truth brings about despair. I think I agree with all of it.
I believe the final message here is to do with the plight of man, particularly NTs who desire knowledge above all else. Mankind's library of mythological and religious stories are replete with tales of those who seek to become like "God", and in so doing meet a bitter end. This story is much the same.