What's the most underrated genre television show of all time?

Everybody raves about Star Trek and Game of Thrones. But what's the great science fiction or fantasy show that never gets its props?

Let us know in the discussion thread below — but please include a picture of your choice, since a picture says way, way more than just a block of text, especially when people are browsing through.

Top image: Dark Angel, but please don't let that sway you.