Compared to Arena, which is infinitely large, then Daggerfall is only 0% as big. But despite being however many hundred thousand square kilometres it is, it seems empty, since it's all just meaningless procgen. Morrowind feels much bigger, because it's actually full of stuff.

You're right about it being legendary - Ubisoft certainly seem to have been inspired by the enormous map filled with really repetitive quests. But there are more important things than size.