Full Metal Alchemist rocks. It's one of the few Animes out there that you can tell was planned out from beginning to end- rather then having a series of story arcs, there is really just one big one.
Do you mean FMA or FMA: Brotherhood?
Brotherhood is an almost exact interpretation of the original Manga, and it's much better.
Al's voice threw me off at first... I really wish they got an adult to do it. Other than that, all the voices sound pretty close to what you would imagine while reading the Manga.
Gianni
I'll tell you who's a bad voice actor.
This guy.
I don't know anything about the actor or the series, but I can tell you this much. I hate child actors. They always suck. Perhaps I'm going a little harsh on kids, but every time I'm watching something and a child actor walks on stage, it trashes the entire experience for me. To the best of my knowledge though, when it comes to animation, they usually use adults to voice kids, with women typically voicing boys.
If for this "Al", they used an actual boy, well then, that's your problem right there.