On Sci-Fi BSG beat ENT only when you compare the best ratings of BSG and the very worst ratings of ENT. Most of the time BSG had ratings far below what ENT had in it's last season. A show can survive on Sci-Fi if the ratings hover at HH 1.5.
The worst ENT ever had was 1.4 and 1.5. Most episodes were more then enough to make it a success on Sci-Fi.