What is that you particularly like about Oblivion, Vauxy? I'm not trying to rustle your jimmies or anything, but I mean as opposed to the things that you dislike about the other games.
Oblivion is a facet of my youth. It was the first Elder Scrolls game I ever played. I loved it. I got lost in it for hours. Sometimes days at a time with no break (I took adderall as a youngster, so that helped). My love for Oblivion is absolutely biased and completely dependent on nostalgia goggles.
Like PP2 said, I do like the quests a lot. I find them interesting and very entertaining. I also think they are more well written than Skyrim's, and just slightly better than Morrowind's. Naturally, going to Morrowind from Oblivion was a weird experience for me. At first I hated Morrowind. I thought it was inaccessible and convoluted. The level up system was basically the same as Oblivion's, so I didn't have a problem with that. I mainly had issues with quest layout, travelling, basic combat, and figuring out what the hell to do. Morrowind, to me, is too demanding and convoluted for newcomers. I started having fun with Morrowind about 30 hours into it. I started having fun with Oblivion almost immediately. Of course, this is a subjective affair but like I said... I am biased.
Oblivion does many things better than Morrowind. The combat makes sense (you don't whiff an attack that obviously looks like it connects), magic doesn't just flat out 'fail', and you can still use weapons proficiently without stacking multiple points in them. The quests are well organized in Oblivion, whereas in Morrowind it is just a complete clusterfuck without mods. The fast travel system in Morrowind is useful, but lacking in comparison to Oblivon's. I know the whole "fast travel is for noobs" argument, but it really helps when you're doing tedious menial tasks. In Morrowind, I had to walk 3 miles every time I wanted to turn in a mushroom for a damn quest. Sure, you could subvert this by using certain spells, flying, and siltstriders, but most of those options are not practical until later in the game. I love exploration as much as the next guy, but when I am focused on one certain task (particularly fetch quests) I want to be able to get it done in a timely fashion and without being side-tracked. Besides that, I don't care about the setting. Sure, Morrowind's setting is more unique and eclectic, but it's still a generic fantasy setting (lol rushy'd) just like Oblivion's Cyrodiil. I actually liked Cyrodiil a lot. I'm partial to high-fantasy bullshit, so it sat well with me and felt natural.
I could go on, but I'll just add this bit. I like the potato faces and the "HALT!" zoomers.