The new Star Trek movie might be a really good way to get them into it gently. It's not shot in a really sci-fi way, needs absolutely no prior understanding, and managed to appeal to some of my most Star Trek and sci fi disliking friends. It's also a pretty good jump into SGA because they're both sort of lulzy fun not taking itself seriously sci fi. I'd definitely not go with BSG because it's kinda a sci fi that hates it's a sci fi, and unless you're really, really into the set up and darkness of the show it can just get hard to watch. It's like Six Feet Under; you know it's really really good and well made, but it's just so depressing.