No, it's not the fanboys that derailed my interest. It's just the seeming lack of something fresh. Yeah, you'll get those fresh and original concepts, but for the most part, it's either harem, or slice-of-life. Also, with the exception of DBZ and a few others, I tend to be a little put off by anime that's longer than 26 episodes, as they seem to just drag on.
Inuyasha was the first I started losing interest in because I felt the story was getting too stale (admittedly, I did enjoy the "Band of Seven" arc). Ouran High School Host Club was an anime I had watched only recently, and I actually enjoyed it because it takes the idea of the harem anime and reverses it; instead of one guy surrounded by a bunch of girls, it's the other way around, except it's more dignified.
I tend to watch more serious anime that lasts no longer than 26 episodes. From Black Lagoon, to Serial Experiments Lain, to Rin, my taste seems to vary, and it's usually the type that few in the mainstream seem to know much about, though that's just what I think.