I'm not a fan of ENT season 4 because 1) it was fan-wank and 2) they kept on ruining the endings on each of the story arcs.
Borderland: Okay
Cold Station 12: Fantastic
The Augments: Poor
The Forge: Great
Awakening: Amazing
Kir'Shara: Poor
Babel One: Okay
United: Great
The Aenar: Terrible
Affliction: Average
Divergence: Urgh
Demons: Good
Terra Prime: Not as good
For this reason I would say that season 3 is the best and season 4 is equal to the first season (and maybe even a little behind it).

