I watched Fullmetal Alchemist then watched Fullmetal Alchemist: Brotherhood.
I can honestly say Brotherhood is EXTREMELY better. you have no clue. I've never had such goosebumps from a show.
watch it monday
This is true. This has probably already been stated by people, but Full Metal Alchemist: Brotherhood follows the manga story. The original FMA series was produced too fast to the point where they made episodes faster than they made the manga. They changed the story about half way through and made it worse (imo).
I watched the original FMA series while FMA:B was about 3/4ths of the way done. After I found out by reading the manga + googling a bit that the original series didn't actually follow the manga, I was pretty disappointed. I watched FMA:B after reading the manga
and watching the original series, and I personally think it was 100x better than the "original" anime.
Definitely worth watching FMA:B if you have already watched the first series.