The intention of this poll is to not consider gameplay at all, but look more at the lands, geography and their culture as if they are real.
For example; one may think Skyrim is the best game of the series gameplay-wise, but may like Hammerfell more as setting, because of the landscape and culture, despite Daggerfall being around 15 years old.
I also did not include the setting of Arena, since that includes all of Tamriel, making the vote very easy.
I think I will choose Cyrodiil. Because of its central location, its geography and climate was really diverse. This also affected its culture, since many races made their home there. Another thing I liked about Cyrodiil, despite the many races, was that it felt as one united province in which all races were welcome. An Orc and Dark Elf had as much chance to become rich as an Imperial or High Elf. It was also an advanced culture with a working infrastructure, Empire sponsored guilds and even a newspaper.