For me, I’d say the choice is close between Daggerfall and Morrowind. Morrowind has a beautiful and foreign world, but Daggerfall has a fantastic and extremely deep RPG system!
Probably Oblivion, although I’m replaying Skyrim right now and loving it.
Something about the atmosphere of Oblivion I just can’t get away from. It’s comfy.
Morrowind all the way. There is an argument that it’s nostalgia as I played it when I was 12, but the lore and politics of that country still intrigue me. Plus I still play it with absolutely amazing content mods like Tamriel Rebuilt.
Arena is a bit of an unfocused mess, Daggerfall is excellent once you get into it, but the issue is it’s difficult for a new player to get into playing it, Morrowind perfectly encapsulates the otherworldliness that fantasy can embody, Oblivion is good, just not as good as Morrowind IMO, and Skyrim is always an enjoyable experience. I’m torn between Morrowind and Skyrim