Yes I agree with you on the point that some places reach an "epic scale", the Architecture of some places is really great.
Though I have to disagree with you about the single most greatest building, because in my opinion the greatest landscape-design and especially the greatest Architecture, belongs to Guild Wars. I have never experienced the "blown away" effect you've described so many times in a single game (when you count the Standallone-AddOns as one game), as I had in Guild Wars.
By the way, it would be really much better if there was an option to disable the HUD. It really takes some atmosphere from the screenshots.