Morrowind was too dark for me. I tried really hard to get immersed in it but the whole look and feel turned me off. Just playing it mildly depressed me and creeped me out, so I never finished.
If you want real classic Elder Scrolls, you’re talking Arena. Which was a great game, with huge amounts of customizability in spells, which led to horrific exploits but was great fun.
I’m with most of the others here - Morrowind captured my imagination enough that I played through it all the way 3 times, once for each of the Great Houses so I could get all of the questlines. The mods for it were excellent as well.
Oblivion is prettier (although Better Heads and Better Bodies for Morrowind helped a lot with that), and many of the game mechanics are more streamlined, but the world didn’t capture me in the same way. I keep wanting to have the Oblivion engine with the Morrowind setting and stories.