Having just spent some significant time with vanilla Oblivion, it's really apparent that the whole environment feels so sterile. Large distances between actual content points, some of those content points barely justifying their existence (Weye, I'm looking at you), and the fact that everything is just too bright.
Though I have to say, seeing those vanilla textures it gave me pause to wonder if many of them really aren't already fairly good and could simply stand to have their resolutions bumped up somehow. At least for the landscape anyway. It's nowhere near as bad as I seem to recall it.
Yes, the meshes do need some help, but not as much as you might think. Straightening a few oddly bent boards and the like would do wonders for cleaning up the remaining poor visuals that aren't outright bugs the UOP has already fixed. Basically a http://skyrim.nexusmods.com/mods/8655 for Oblivion.