With the success of BSG among sci fi fans, QUOTE]
What makes you think the new BSG was a success among sci fi fans?
From what I've observed it was really getting massive criticism from fans for its last couple of seasons and was never a huge ratings winner.
BSG suffered from production issues, having a six year span, for what amounts to two regular seasons causes more than a few issues.
BSG whether or not it is a ratings success is a major game changer to sci fi as a genre. Terra nova, and SGU, are obvious proof's of this.
As far as the darkness of bsg, I think your out of the loop. Shows like breaking bad, sons of anarchy, rescue, mad men, are all dark as well. When you factor in our recent love affair with disaster films it fits right in.
Granted some of the filler eps did meander into some really blah episodes, but it had nothing to do with darkness.