I've only played Oblivion, Morrowind and Skyrim
I was never able to get into Morrowind, the combat felt extremely clunky and even with mods (back when) it looked trashy. But there was a certain charm to it. I'll give it an honest second chance one day.
Skyrim... has the best melee. It has the best visuals. The best levelling system. But... it feels so lifeless. The quests are dull, the environments are dull, and man I hate to say it but the soundtrack minus The Dragonborn Comes is pretty forgettable. The perk system had so much potential and yet it all basically comes down to 'take less and do more damage' and of course 'easier sneaking and lock picking for the same amount of effort that it would take to become a master of magic'. And STILL NO ACTUAL NECROMANCY SCHOOL AND SUPPORT. Nobody cares about having one or two daedric summons, Bethesda. NOBODY.
Oblivion has that bright, typical fantasy landscape going on. Which is super comfy. The quests of the vanilla game are... well, better than Skyrim, but not very great in general. But it does have THE DARK BROTHERHOOD. And THAT THIEF GUILD FINALE.
Mage Guild is very boring, same with the fighters guild. BUT. Unlike Skyrim, you actually get spell crafting. And who cares about the fighters guild when you have Knights of the motherfucking Nine. Too much generic fantasy after a while? SHIVERING ISLES.
I love Oblivion. I think it turns 10 years old this year too, so I can actually forgive the unexciting combat due to being "old". And the horrendous levelling system that encourages you to never ever level up and how even the poorest, weakest of bandits will end up walking around with a full set of glass armour, hit harder than any daedra that was threatening the lands at the start of the game, and still ask you for a measly 100 gold or your life. And how every vanilla dungeon feels exactly the same. (Okay, mods fix all that since forever ago so it's actually a non-issue but it had to be said).
it was meant to be a joke city full of nazi stuff but it ended up thriving and becoming a high-income megalopolis...