For me, Oblivion was the first of the TES series I played. Once I discovered mods and the ability to shape the world to my optimal experience I spend so many hours, until replaying become less of an option due to having been everywhere. I don't really like custom content, just immersion-improving mods and gameplay tweaks. So eventually I considered playing Morrowind, seeing it should contain a vast amount of content I hadn't seen yet. At first I have to admit it was really difficult to get into it, in the same way I got into Oblivion. The way you interact with people is so different (you click on 'topic links' inside text) and the difficulty curve for combat is different because it relies more on stats than on your actions. After a while though, it got better and better. With various mods it can look as good as Oblivion and the unique setting of Morrowind makes the world so much more interesting than Tamriel. I remember going into the smugglers cave just outside the starting town, I died 3 times before I got through it, and it was so much more exciting. I'll see if I can find a list of the mods I use and really recommend on trying this game. There's so much depth and if you can get past the initial lack of features you're used to from Oblivion, you will find it difficult to choose between the two.