I don't hate Oblivion, I even enjoyed it while it lasted. But it never left any major memories, apart from the DB questline (and 'Whodunit' in particular), the Arena announcer and maybe the final thief quest. Everything else is just a big bland mix of potato heads, glass armour bandits, grey stone buildings/dungeons and green hills. Oh, and an Oblivion gate here. Oh, and there. Ah, and here too. Ok, **** those Oblivion gates, seriously.
I thought I'd be all over it after Morrowind, but it just felt terribly bland, and it didn't help that the Spellmaker got butchered too. And something just doesn't work scale-wise. If I remember correctly, it is technically bigger than Morrowind, but it sure as hell doesn't feel like it. Thanks to its geographical design, draw distance limitation and lore-friendly fast-travel options, Vvanderfell felt big and going from one end to another, or into some forlorn coastal/mountain village was a trek. Vivec itself managed to feel like an immense maze and Mournhold itself was ok. In Oblivion it's either zero-lore clicking on a marker, or beelining to destination on horseback. It ends up feeling so tiny that it's difficult to feel out there when all those major cities are so close to each other, and the scale is just off for the Imperial City we should have been losing outselves into but feels more like a couple FPS deathmatch maps.
At the end of the day, I find Morrowind more entertaining for the world and builds, and Skyrim a better/prettier alternative if I'm in action-TES mood. I think Oblivion is the only mainline TES game since Arena I never felt like revisiting (I say mainline because I never managed to will myself too far into Battlespire at the time).