I have played through morrowind several time over the years, and every time I play through Im encounter little things, and even quests i never found before, probably due to character choices or faction quests lines that split off. I can even say there are areas of morrowind/bloodmoon and tribunal expansion that I have never explored due to the sheer size and scope of the places. Every time I play I wonder what I will discover for the first time....
I dare say that Morrowind + expansions is the best single player experience Ive ever had. If only Zenimax could recreate that experience in ESO....