Some SF movies have been popular of late - and most mainstream films have become more science-heavy... but people that watch these shows are in no way fans of the genre. I don't know of any Mainstream types who read SF books regularly or who avidly watch more than one or two of the most main of mainstream SF shows/series.

By contrast, even the non-uber-geek SF fans will know a Ferengi from a Centari by sight, will understand what the odd-even rule is and can probably rattle of the three laws of robotics (plus the extra one) on the spot. These are the people I mean - and I still think there's a difference between them and people who may have just watched The Matrix, LOTR or one of the X-Men movies.

Actually being part of the full on SF fandom culture is definitely non-conformist. Think trekkies (or trekkers if you prefer).

And by role-playing gamers... I don't mean video games... I mean classic dice-rolling "your elven warlock spots three kobolds" kind of role-playing games. WoW is a different kettle of fish... but I know of nobody that thinks classic RPGs are "mainstream".