1. Elder Scrolls
I don't believe it's actually possible to write any list of games without including, or indeed closing with Bestheda's Elder Scrolls series. The prelapsarian landscape of Tamriel is explorable throughout the different installments of the series and for the sheer scope of the possibilities for character progression, introductions to NPC's who live their own lives with their own personalities. Fallout, the sister series to The Elder Scrolls also features a fully interactable environment but at times the sparse nature of the wasteland made me feel isolated. While parts of Morrowind felt replicated, the formula was almost perfected in Skyrim which featured constantly striking examples of forests, snowy dunes and city ports.