Compared to many films showed at the cinema, tv shows like BSG are pure masterpieces writing-wise!

As for Ellen I agree with you in that I don't think the mystery about the Fifth has ever been the point. The show has always been about defining humanity, about what makes us human. The Cylon Machines vs Mortal Colonials was a plot device, or rather a dialectical method, and the parallel between the two societies have been legion.
Cylons used to be Greek gods, now they are mortal, but Kara's weird journey and the Final Five storyline carry on the mythology that helps talking about humanity through sci-fi and fantasy.