The Elder Scrolls

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.

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

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.

Going just by 4 and 5, I choose Oblivion. Oblivion's quests and characters felt more personal and whimsical.
Skyrim was like... hostile. Seriously, Skyrim is not an inviting RPG place and you certainly won't feel like a hero.

I probably have a bit of recency bias, but I'm a massive fan of ESO. It has the most lore, great storylines, better models than oblivion or skyrim, and takes place at the earliest date of any game in the franchise.