I'll just make a (short) list of why Oblivion is/isn't as good as Skyrim, in my opinion.
It is better than Skyrim because:
If you're a mage, it's better in every single way, from custom spells to the power of spells, to armor effecting your ability.
It's much more customizable, besides custom spells, there are not only more outfits (actual outfits, not sure about armor), but pants and shirts are actually considered separate, so you can dress your character however you want.
Puzzles are a little harder (they are still easy, but they don't usually put the answer to the puzzle DIRECTLY BEHIND THE PUZZLE OR ON THE KEY like they do in Skyrim, cough cough, please excuse the yelling)
Attention to detail (to some degree). Armor and weapons break if you don't do maintenance on them, sure it takes ten seconds to do the maintenance but still, I appreciate the attention to detail, it makes it more immersive.
Graphics: It looks like an actual fantasy game, set in a fantasy world. No, it's not "photo realistic" and on some level, I'm glad it isn't.
Varied environment: Snowy areas, swamps, forests, a capital city that looks and feels like a capital city.
It isn't better than Skyrim because:
It's a lot easier. I've been able to almost completely finish the main story, having already completed the storyline to several of the guilds as well as becoming arena champion all while at level one.
Gold (or lack thereof): Get used to being poor when you're at lower levels. I seem to remember it charging you for enchanting too, which is lame. Want to create a custom mage's hood but only have one hundred gold? Well your high enchanting skill plus your filled grand soul gem will allow you to enchant your mage's hood to give you a whole five extra magicka points.
Repetitive dungeons: Two words to sum up almost every dungeon you'll encounter: Turn Left.
Graphics: Most of the characters can be described as "ugly" and it does look dated overall.