imv oblivion had quite screen shot happy landscapes, especially with a few mods. The issue for me was the lack of wilderness. In that you were never more than 5mins horsey ride from a city. The landscape, interms of geomorphology was far more heterogenous in oblivion than morrowind. There were distinct biomes, swamps mountain etc. but the size and shape of the hills spacing of ravines, and the very few small streams and lakes didnt create individual characters for the differnt areas. In morrowind theres a big difference between the plains, the island archipegiallos, the bitter coast, the red mountain, and the area around genesis etc. In oblivion, if you took the vegetation away i dont think there would be much difference between the gold coast and the dark swamps.
to continue, they varied the architecture of each town, but they all contain pretty much the same set of shops and services, i didnt think there were enough small villages or different styles of cities. In morrowind the settlements could be very different. Balmoral was very different to Aldrun. Rather than just having one city per architecture/cultural area of the map, there were often two or three, this made the regions feel more real, than generic city with different colour roofs that you got in oblivion. The characters in morrowind were written to have feelings about the different geographical areas, in oblivion theres less of this, just abit of racisim.
Morrowind also had tones more mission content. In oblivion vanilla, theres what, a main storyline, 4 guilds, and misc quests (imo some of the misc quests where by far the best). In morrowind theres 3 houses (i felt the houses brough alot to the character of the game, gave it interesting politics etc). 4 guilds (there could be more that i havnt done, ive heard rummours etc), two religious sects, and the legion, plus lots of misc quests. In oblivion you coulfd get about two characters through the game before you'd done verything. In morrowind, ive done about 8 characters and probs 100+ hours and still have never done the morrag tong, or telivani, or legion quests through to completion.