Flash Forward was pretty good, though. I saw it on DVD and was getting really into it when they canceled it.
Jericho's cancellation was one that really hurt. Cable should have picked it up. You can think of a lot of today's post-apocalyptic TV -- Walking Dead, Falling Skies -- as sequels.
Dark Skies should also be on the list. It wasn't just a sci-fi show. It was also a pretty good [alternative] history show. There were limits to how far the series could actually go, I guess.
Harsh Realm, a show about virtual reality, should also have gotten a better shot at success.
Harsh Realm, and aanother DB Sweeney show, Strange Luck.
http://en.m.wikipedia.org/wiki/Strange_Luck