Come to think about it, all of the most famous Build Engine games (Duke Nukem 3D, Shadow Warrior, Blood, Redneck Rampage) feature much more realistic level design compared to the DOOM and Quake games.
Thus it’s got to be something more than just the style of the designers who worked on the levels (because these were different people); there must be something inherent to the engine, or the editing tools, that make it much easier to pull off realistic-looking environments.
