Totally my opinion coming up. Also, I tend to sound more definite than I am. This is enthusiasm, if anyone's wondering.
I think Oblivion gets an unfairly bad rap. The series has gotten casualized... But when I first played Morrowind, I was disappointed by the lack of character "special power" customization. "What was this birthsign thing, and it sucked!" I was disappointed by the lack of climbing, by the tiny dungeons, and that the spellmaker could only make spells based on effects you already knew, despite the fact that they were the one making spells, broke my immersion.
But it had a weird and creative setting, interesting stories, neat powers to acquire, could still roam everywhere, and levitate softened the lack of climbing. And I learned to enjoy it, and grew to love the setting.
And yeah. My first and long-lasting impression of Oblivion was "they made everything bland and generic! You're fighting an invasion of demons in Generica!"
And to an extent, you are; it is generic. By that scale, it sucks compared to Morrowind. So eventually, I stopped comparing it to Morrowind.
Because Daggerfall was the best Elder Scrolls game... And it's got plenty of generic-looking places. And I ended up enjoying Oblivion for what it was: A well-done fantasyland, with hidden depths and its own weirdness; with combat where you can almost feel the impact of each blow, and manoeuvre, tactics, and strategy are visceral and in-the-moment. Oblivion has been casualized, to an extent...But being cornered by two Dremora Churls at level 5, nearly dying in the process, and then cornering them and beating them down, having one of them run
, doesn't feel casual.
Taking out levitate, and making almost every dungeon double back on itself, even Oblivion Gates (especially Oblivion Gates)...Yeah, casual. But at the same time, not, because it allow the designers to set up puzzles and traps that they couldn't have if you could just saunter (literally) over them. Those Oblivion Gates would be a lot easier if I could just fly up to the top of the Sigil Tower, kill the Daedra inside, and then grab the Sigil Stone. And a lot more boring.
I also like the lockpicking game; it feels like lockpicking; or what I suppose lockpicking would feel like. The persuasion game... Not all that bad. Joke, boast about yourself (but in a clever way); even taunts and threats can be friendly between buddies.
But yeah. Losing medium armour sucks. Losing the ability to enchant your own items sucks - but your odds were generally really low in Morrowind. And finding out you needed soul gems now to enchant in Morrowind? That was a "bleh" moment.
tl;dr - All the games have good points (and things they maybe could have done better)