Um, backpedaling with a series like TES is often hard, just because you will keep on thinking about what is missing in the previous game that was in the present game.
For example, you will likely miss the use of physics, shiny graphics, and most likely the battle system.
However, if you push past that, you will find that Morrowind is a much deeper and, in my opinion, much better.
There are lots of mods to help with the lacking graphics, such as Ren's Beauty mod and Better Bodies, the first of which adds pretty faces and the second of which adds better bodies. There are also high res texture mods and other small mods that give the game a nice feel.
As for other content, the game has been out for a while so many quests, items, equipment, houses, and places are available for download. Just look for a good site with a decent rating system so you don't have to sift through all the crap.
Or, you can just fire up the TES Editor, which is a very easy program to use, to create your own mods.
I repeat: Morrowind and Oblivion have very different feels to them, and just because you like Oblivion doesn't mean that you will like Morrowind. A lot of fans of Morrowind disliked many facets of Oblivion.