So right now, Defiance is basically marginally at the top of the heap. Sure, there's a couple of projects that might challenge this - Bryan Fuller's Syfy show, the Swedish series Real Humans, hell, maybe those remakes of Blake's 7 and Space: 1999 might amount to something - but right now this is it.
After episodes 2 and 4, I might've agreed with you about Defiance
's relative quality. But I've been increasingly disappointed by the past three, and right now I have a very negative opinion of the show. Maybe more negative than it deserves, but I'm bitter because my hopes were so high.
Although I'd still put Warehouse 13
at the top of the heap, except it falls more under fantasy than SF. But there's also CBS's Person of Interest
, a solid show that's become more overtly SF over the course of the past season.
As for Orphan Black
, I've heard good things about its quality, but also heard that it's a darker show than I like to watch -- which is also what keeps me from sampling Game of Thrones