According to Airlock Alpha, all the returning genre TV shows came back in 2009 to smaller audiences than in 2008.
"No genre show finished below a 2.0 household rating average in 2008, with "Supernatural" attracting the smallest audience with a 2.1/4. However, three shows finished below that threshold in 2009 led by the now-cancelled "Reaper" on The CW with a 1.4/2 followed by "Supernatural" with a 1.8/3 and "Dollhouse" on Fox with a 1.9/3."
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Source: Airlock Alpha.