I don't hear of anyone talking about Cyrodiil in Morrowind?
Plus Oblivion Cyrodiil has swamps and stuff.......Leyawiin area. The entire southern part.
Also, the "generic landscape" stuff is just crap. What else you want? Its a forest.
Click the "Cyrodiil" topic in a conversation with an NPC that has it.
Here's what you'll get: "Cyrodiil is the cradle of Human Imperial high culture on Tamriel. It is the largest region of the continent, and most is endless jungle. The Imperial City is in the heartland, the fertile Nibenay Valley. The densely populated central valley is surrounded by wild rain forests drained by great rivers into the swamps of Argonia and Topal Bay. The land rises gradually to the west and sharply to the north. Between its western coast and its central valley are deciduous forests and mangrove swamps."
Notably--and you can check this against the first edition of the PGE, which the lore text was based on--the Heartlands are still part of the Nibenay Valley, and though the central islands are grasslands, the lake itself is surrounded by a rainforest--and the forests grow thicker and more swamplike the further south you follow the Niben River.
What Oblivion did was take the climate of the Colovian highlands (foresty and such) and place it all over. Yes, the very southern ends of the Niben are jungle like, but even then, just barely.