@M.ComicFan for example, the first Fullmetal Alchemist anime from what I heard, heavily deviated from the manga(due to the manga not being finished)...the Brotherhood anime stuck closer to the source material. Weirdly though, I liked both versions- but I (kinda)hated that they had to make Shamballa; I liked the first series ending the way that it did.
Manga that I invested in: Silent Mobius, Battle Angel Alita, You're Under Arrest, Oh My Goddess, Gunsmith Cats, Dark Angel, and Steam Detectives...I was a big Asamiya, Fujishima, Kishiro, and Sonada fan.