[BranjoHello]

I played Morrowind for about 750h without finishing the main story (Later I created another game where I focused just on main quest), that alone can convince anyone how great the game is. I just felt so immersed in the world it was so believable, just calling for me to explore it more and more (pixel y pixel). The NPCs maybe weren't many but almost each one of them had soul. Visually it was one of the best games on the market when it came out. And the music, my goodness, I still listen to it now and then in winamp.
Oblivion is good but the random dungeons and stupid leveling of the world with your progress killed a lot of the magic. About 300h spent there.
I'm now playing Skyrim, 80h in it and it is just thrilling, the world is great, combat is challenging (I'm playing in Master difficulty) and the things that are made "easier" from previos installments are like that in a good way.
As for Arena and Daggerfall, I'll probably never finish the first one (tried 2 times and couldn't play it for more than 10 minutes) but I have high hopes for Daggerfall, curently I just finished the first dungeon and traveled to civilization. Not much mileage there.

@Japo
Are you 100% possitive about Morrowind having the choise of difficulty? I don't remember that.