I was recently faced with a decision. I have never played Morrowind in detail... only the first town and some random wandering around before I put it down when I was a kid. I've never played Oblivion at all, but I have played Fallout 3 and loved it.
I looked at TESNexus and Planet Elder Scrolls and decided that the game mods for Morrowind are better than Oblivion. It's mostly because of the age of the games, but still.
I beefed up Morrowind with a series of mods. Bug fixes, tweaks, classes, factions, faces, textures, character models, the works. The mods I have add more flora and fauna, including better looking trees and more plants, animals, dogs, adds more workers to farms and more animals to farms, creates more water life, etc.
I've changed how my character levels, added more depth, more areas to explore, more geographical features like waterfalls and mountains, added more quests and tons of new balancing mods. There are mods that add new items, weapons, armors, and add new abilities like armor smithing, arrow making, poison making, better enchantments, better alchemy...
Overall the mods I have have brought Morrowind into this century nicely.
All the mods I have, however, have more than tripled the game's initial load time.