Suffice to say, while I prefer Fullmetal Alchemist out of those three, Naruto is probably the most popular series right now. Once Fullmetal Alchemist has its movie dubbed and brought over to the United States, then it will most likely die down as well. Inuyasha has its popularity going down (you have no idea how thankful I am to not have to see fangirls and fanboys claim that this piece of crap is a masterpiece).
Basically, Naruto looks to be the only series out of the three to maintain its popularity for the long run right now.