Stunning real world. Gothic 3 and Oblivion 4 are my first and only RPGs tried, so that is my only benchmark.
This is the kind of game I have been waiting for: An plausible open-ended atmospheric world with a realistic and very convincing landscape. The only previous game where I thought that maybe this genre was starting to appear was Morrowind, which I observed but never played, but this seems technically streets ahead.
Do not be mislead by its poor "player rating". Its low score is skewed by those users who could not get it running (pre-patch?) and gave it 0 or similar. The "median" score is probably nearer 9. Note however: You need a good video card (X800+) and preferably 1.5 gig or more memory. I have run it well on a Sempron 3000+, X800, 2gig ram. You also need to follow the helpful tweaks from the forums, but the effort is worth it.