Well, it helps to distinguish between the two types of otaku. First, there is the Japanese definition: A shameful outcast with an unhealthy obsession, often lacking social graces. Secondly, there is the English speaking definition - like a geek: Proud of their interest (usually obsessive) in something.
In the second sense I can go overboard with anime, graphic novels/manga and books - science, science fiction and fantasy. You might have seen my manga bookshelf, but the other five are overflowing with paperback and hardcover novels,
Analogs and
Asimov's. I would call myself a Portal/Portal 2 otaku, having played each dozens of times, but only those two games. I have played about 10 visual novels/eroge but those are not a big part of my life. I was a heavy metal otaku in the late '80s and early '90s, but my musical tastes have branched out a lot since then. I know a lot about silicon chip fabrication, but that's work and not play. I'm also a bit of a beer snob, liking specific imports and microbrews over the love-in-a-canoe brews
[1] many other Americans prefer. I can recognize a handful of seiyuu voices from show to show, but Atsuko Tanaka and Kugimiya Rie are the only two names that stick in my head.
TL;DR Anime, graphic novels & manga, books, Portal/Portal 2, good beers.
[1] (fucking close to water) 
