I'm such a supernewb anime-watcher, but I finished watching FMA: Brotherhood in 2 days. I expected it to be childish, based on the few episodes I saw of the 2003 anime back in high school, but it got pretty crazy. I gushed over the creativity of some of the action scenes, and I appreciated the author's attempts to keep believability in balance. I don't know where FMA ranks in the anime world, but I was taken by surprise from nearly all angles. The depth of the narrative just kept on surprising me, dancing around the threat of becoming convoluted but never quite breaching it.
That said, the first half I loved watching because I craved answers to all the questions and because I loved seeing the characters develop. The second half I just wanted answers.. because it felt like the author lost some of his tight narrative focus. We saw less and less of the Elric brothers, less adventuring, less jokes. It was weird, and it felt a bit "off" as a whole.
So Deathnote, DBZ, and FMA:B are what I've seen so far. I have more praise than complaints by far.