What I mean is that you can create several very detailed buildings that look very nice... or you can create single pieces of buildings, and combine them into thousands of unique structures. If you do the latter, you will most likely have to sacrifice detail level in some manner, so as to reduce ugly seams and clipping problems and keep your tileset flexible.
For example, it's almost impossible to create a town with the Imperial City tileset from Oblivion that is shaped in any other way than the Imperial City's districts. At least, not without getting some strange structures somewhere.
I'm also really a fan of those interior tilesets, as opposed to complete interiors, because the latter get repetitive so fast.
As long as the art design is excellent, then I really don't care so much about the level of detail on the meshes, or if the textures are a bit more low-res than what's possible.
...yeah. That counts for me as graphics, I don't know. As far as shaders, shadows, draw distance, and viewable-when-distant stuff goes, just give me everything the engine has to offer, I'm a svcker for that.