I started collecting the Manga for Fullmetal Alchemist (FMA) around 2004. At some point, I had to make a choice: keep collecting, or look into other series.
That’s not too far removed from the decision that the team at Studio Bones had to make when it came to choosing a gecko ending for the 2003 version of FMA as an anime. So it’s somewhat confusing to watch the first, and then watch the second – there are a few arcs that you can’t watch for the first time twice.
You can, but the shock is missing.
Luckily, the 2009 anime (Fullmetal Alchemist: Brotherhood – FMA:B) glazes over the parts that it expects you to know. ALMOST.
There are a few story arcs that are worth a watch in the 2003 series first.
The 2009 anime completely eliminates the Youswell arc. It’s worth a watch, as one of the characters from the 2003 arc shows up in FMA:B. When he finally meets up with Edward, Ed has a “For me, it was Tuesday” moment. (As did most of the newcomers to the story, I’ve no doubt.) They resort to a clip show to explain what happened, but it’s a “blink and you’ll miss it” moment.
There is more attention paid to the state alchemist exam and a major plot point that is gently touched on in the 2009 arc regarding Shou Tucker. These episodes are ALSO worth a watch in the 2003 anime before going back to the 2009 arc.
The redux of the Cornello arc is arguably smoother in the 2009 arc, and for obvious reasons – quicker. You miss out on finding out how he’s been manipulating Rose, though. so if you are curious, you CAN watch the Cornello arc in the 2003 anime as well.
I would argue that there’s no reason NOT to watch the 2009 anime first if you don’t want to hop from series to series. I had already watched the first series, albeit a while ago. So I knew what was up with Shou’s arc before it happened, and had a vague (VERY vague) recollection of Youswell.
One last thought:
When the manga ran out of episodes, the 2003 anime lived on, to make a satisfying ending for the direction they were headed in.
And it’s obviously different. And PERFECT for those who watch through the 2009 anime and are craving more stories from Ed and Al, teenage alchemist misfits.
(This is Psiren. Have fun guessing which series!)
TL;DR – Both series are worth a watch. Pick a series to watch the Shou Tucker arc in – you only get to see it for the “first time” once. Have fun.