Observations and philosophizing follow.
Anime fandom, unlike the media fandoms that came before it, is not exclusively rooted in SF/fantasy, and I think this is pretty significant. While it is true that the anime that gets all the attention (Akira, Cowboy Bebop, Inu-Yasha) have strong SF/fantasy elements, there's quite a bit of anime and manga that has no SF or fantasy elements: no magical girls, no robots, no giant suits of powered armor energized by alchemy. Just school kids/adults coping with life and its daily insanities. We're talking Maison Ikkoku, Marmalade Boy, His and Her Circumstances, Ai Yori Aoshi...the list could go on for a couple of pages if I wanted to do the research. So there are anime fans out there who have little or no interest in fantasy or SF, because the medium isn't exclusive to those genres any more than TV and film are.
Anime fandom seems like a weird cross between normal SF/fantasy fandom and media fandom...most anime fans seem to be mainly interested in cosplay and the dealer's room, in that order, and not so much in panels. That lines them up with media fans. On the other hand, there's also a strong antipathy for the kind of "corporate" convention that media fans are apparently willing to accept (CreationCons, frex) with much hostility being expressed towards A-kon and the idea that we're charging $50 at the door for Anime Detour so we can line our own pockets. (As if!) There's a lot of support for fanart in all its forms, not just fanfic: fansubs have long been a part of the anime scene, and there's also a lot of fanart being exhibited. Anime fandom also has a lot of crossover with console gaming, which is not too surprising considering that popular games from Nintendo, Sega and others have been made into anime while the reverse is also true, with Ranma 1/2 and Inu-Yasha fighting games being avalable. So, you see a lot of Final Fantasy and Kingdom Hearts costumes in the cosplay along with more widely-known characters from popular anime series.
Another weird spin on this is that while with previous media fandoms you had an underlying base of written SF and fantasy, the reverse is true with anime fandom. Even though the source manga for anime exist before the anime in Japan (with notable exceptions such as Revolutionary Girl Utena) in many cases the anime comes out in America and only after the anime is successful does the manga appear. Yes, of course there are exceptions, but for the most part the anime comes first and then the manga, in a reversal of the "normal" pattern.
There's a lot of interesting cultural stuff to be examined here, if a sociologist was interested. Much could be made of the fact that unlike SF, which in many ways is uniquely American (and please, don't lecture me about colonials like Stanislaw Lem, John Brunner, et al), anime injects a whole raft of different cultural assumptions into the consciousness of its viewers. Anime has hundreds of years of separate history behind it, filtered through the mindset of a modern society that hasn't come to terms with its role in World War Two or the Sino-Japanese War that preceded it; a modern society that underwent an abrupt and violent transition from feudalism to German-style monarchy and then another equally violent transition to parliamentary democracy at the hands of American general Douglas MacArthur. What kind of effect does seeing the United States through this ambiguous lens have on high-school kids? Do the different roles of men and women in anime's depiction of Japanese society affect how male and female otaku see and treat each other?
A lot of food for thought. It's going to be interesting, watching this at close range over the next few years.