The Wire is ace, though the storyline with McNulty in teh last season nearly took the sheen off it a bit.
BSG is also ace, though flagged badly at times (remember the 'detective' episode?). Wish there was a lot more dark, grown-up, straight sci fi. Really wish someone would make a series out of the Ian M Banks culture novels - would be very hard though.
Farscape and Firefly? hmmm.......
I'm currently massively obsessed by Game of Thrones, can't wait for the next series.