Don't get me wrong I love most Sci-Fi stuff but, I think I geek out on stuff that no one else likes. I think thats the point really. Thats what makes it Geeky. When you're hobby annoys the life out of everyone else... thats geeky. Showing up to Comicon Dressed as Wolverine may not be as geeky as you think.
Star Trek the Next Generation was one of the most popular TV shows of all time. And in a way still is.
I geek out on stuff that no one else is into. Kind of like those END TIMES geeks or like James May...
I guess its not that loving something makes a person a geek about something, I feel like I can
"go there" about: Star Trek, Star Wars, Stargate, Veronica Mars, M.A.S.H., X-Men, Power Rangers, Lord of the Rings, Disney Movies, NES games, Super Nintendo Games, Goldeneye (both), Gran Turismo, Xena Warrior Princess, Highlander, MUDS, Final Fantasy 11, World of Warcraft, Diablo, Mechwarrior, HTML, Alice in Wonderland, Q-basic, C++, Pogs, Magic, College Football, Madden, Porsche, World War 2 fighter aircraft, Pilgrim's Progress, Narnia, Frank Peretti, Shane Claiborne, Kierkegaard, Way of the Master, etc.
Those are all things that people will accept if you casually bring them into conversation. No funny looks, perfectly acceptable to assume that maybe someone has a fond knowledge of some of them.
But to Really geek out about something for me its got to be a bit off the beaten path, like, NENA, Paradise Lost, Deconstructionism, Verliebt in Berlin/Le Destin de Lisa, Communication Theory, Non-existence of time, Undersea Acoustics, where finding someone who knows how to Geek out about these sort of things is like being in Mongolia and stumbling across someone from your Childhood. I'll turn into MovieFan about most of these things.