The impact that FMA-2003 has is on a different level. The goosebumps, the heart pumping, the confusion, the anger and the gut wrenching feelings of injustice are just different. Brotherhood had the classic anime ending we want of the good guy winning. It had a plot that was easier to follow. FMA-2003, without giving away spoilers, was and still is one of the few animes that show that overcoming the porblem doesn't mean everything will be set back right.
The journey was different, though the end goal was the same. Going through the journey with Ed and Al the first time had me desperately following them along, eager for them to get the happy ending they wanted. I flinched along with them, cried along with them, pumped my fist for them. It left me with a hole in my heart but a bittersweet smile on my face. In Brotherhood, it was like I was walking beside them and sometimes pulling ahead and impatiently waiting for them to follow. The urgency and genuineness of their plight fell a bit short (but that's not really saying much since Brotherhood still pulls up better than most animes) in comparison.
Brotherhood is the closure that you need after watching FMA-2003 because it neatly ties everything together. The beauty of FMA-2003 was that it left everything open ended, that I could imagine and learn from Ed and Al what going through life means. Sappy as it is, FMA-2003 shaped who I am today because of the lessons of morality and human nature it showed me.
If you haven't watched this anime yet and are thinking of doing so, I can't promise the same impact. The art and sound were brilliant when I watched this back in 2005 but rewatching this may not be up to par if you compare them with the 2010s anime. However, I guarantee that the characters, the story and the enjoyment of this anime will still be 10/10 no matter what year you watch it.
