I've got to somewhat agree with Gaith in that I'm not as up on Demons/Terra Prime as most of the people around here, but I can't really argue against those who've laid out their reasons for disliking TATV, particularly when the episode's own writer doesn't even defend it anymore.
I don't really like the "epic" finales/season cliffhangers, so my choice for ENT's finale would have been...."Observer Effect."
Yes, it was a bottle show. No, it didn't have massive space battles. But it had some great character moments and Archer's speech at the end really laid out the case for the human adventure.
With a little revision, it would have made a great finale, given what we'd seen from ENT over four seasons. Maybe a last scene with Archer getting a subspace message that he's to come back to Earth to help negotiate a treaty between the Vulcans, Andorians, and Tellarites, and the Observers remarking that yes, humanity does have potential. Dissolve to the three captains giving the monologue, and it's good for me.