Never ever watched Firefly, so I have no idea of the attraction. I think I've seen a movie on it, I think it was called Serenity or something. I'm probably going miles wide of the mark, though.
BsG, only watched a couple episodes, it seems interesting enough and the Cylons look damned cool, but yeah, I still need to get around to sitting down and watching it.
Star Trek, aside from the very original series and most of the movies, I've watched all the other series. TNG, Voyager, DS9...And the newer one, I think it was called Enterprise? Didn't like that one as much as the older series.
I don't think I've seen a Star Trek/ MLP crossover yet. I've seen so many crossovers, the best probably being Fallout
. And, hey, just look at the banner of that Fallout link. Diablo 3, right there!