1. Story:
Sorry, Oblivion's story was awful. You're not even the protagonist in that story. You think you're the hero in Oblivion? Wrong, you're the hero's stooge. The beginning was promising, but the pacing of the story was so far spaced out by the need to complete menial tasks, that anything remotely epic was instead hollowed out completely by it. Oh yeh, how do you know you're not the protagonist? Think back to who actually defeated the source of all evil in that game.
Sorry this is a joke right? Was Frodo the hero in the Lord of the Rings? I don't know? He wasn't the king was he? Just because you're not Martin doesn't mean you aren't the Hero. The Hero is the person that does the acts, Martin didn't do much really, other then right at the very end he does 2 things... compared to all the things you did? No, you're definitely the Hero. Also at least Oblivion had epic moments, Skyrim is seemingly lacking in this area.
2. Environment:
Cities are MUCH more unique and well crafted. This is where I believe quality >>>> quanitity. Every major city in Skyrim has a unique story and houses a different major faction, not to mention art design. Playing in each city in Skyrim feels unique.
Another Jokes, 4 of the MAJOR cities in Skyrim use almost exactly the same Inn, Jarl's House and generic houses. The only Unique cities are Solitude, Markarth, Windhelm, Riften and I hesitantly say Whiterun as it still uses a few far too common prefabs. Falkreath, Dawnstar, Morthal and Winterhold have very little uniqueness, at least in the buildings they use. I believe even the burnt out house in Morthal is mirrored in Winterhold and Winterhold's only real unique feature is the college. I don't think there is anything really unique about either Morthal or Dawnstar at all. Oblivion's cities were more unique, larger in-size and had vastly different lay-outs. All of skyrim's cities feel small and underwhelming, in fact they don't even feel like they compare to the smallest of villages...
3. Dungeons:
The scale, the design, the variety. All in all much much better. I remember this particular random dungeon one of the sidequests in Solitude sent me to. As soon as I entered into the second level, the whole dungeon opened up into a huge underground abyss with a high tower centering the landscape and a necromancer drawing energy from the entire cavern, filling the massive cavern with gleams of blue light. A spectacle! Yet there are so many like this.
Skyrim does have better dungeons, however there were mistakes repeated from Oblivion, mostly around over-usage of very limited amounts of prefabs. There are new issues however as well, while the dungeon design might be impressive, mob/NPC layouts can be terrible, too many Draugr only dungeons in Skyrim at least Oblivion mixed up it's mobs/NPC more which made things more interesting. Also too many mobs are simple push-overs with only one overpowered boss at the end, not much in-between really.
4. Quests:
The main quest is better due to the fact that the story is much better this time around. Guild quests are shorter, though still very good. The biggest change is in the side quests. For one side quests take place in skyrim's dungeons, which makes them more enjoyable off the bat. Secondly, I feel that more lore is placed in skyrim's dungeons. There are also quite a few twists attached to side quests, more than in Oblivion.
I don't agree, I'd say the story this time around is worse, it maybe better written but it's poorly executed mainly from the fact it's too short and too easy. As for guild quests, they don't feel like guilds so it's not even good, let alone "very good". Skyrim does have undeniably better side-quests, but they've come at too much of a cost to the main quest and guild quest lines. And no, saying you should go do other things doesn't count... for a very good reasons which is that I did go and do other things, but when ever I return to the main quest and guilds, there was still too little substance to them.
5. Creature Variety.
There are more wild life variety. There are more unique monster types.
There is, but you'll still end out fighting more draugr then anything else. Second place goes to Falmer. Oblivion mixed it's dungeons up a lot more, you had Lich, Wraiths, Skeletons, Zombies, Necromancers and ghosts all in the same dungeon or you got Conjurers, Atronach, Deadra, Skeletons and Mages. In Skyrim you get Draugr or you get Falmer, Chaurus and Automatons or even worse, you just get conjurers and Atronach... Skyrim has more mobs but it does not use them as well as Oblivion used it's slightly more limited set of mobs.