I played skyrim for about 100-150 hours, and watched a streamer play it for around 500 hours, and I maintain that Oblivion is better...if only by a small margin. But then if you throw in mods, there's really no contest at all. Oblivion is better, and it will always be better.
Even in some ways most people might not expect. For example, I actually find Oblivion to be better looking, in general, than Skyrim. Sure, there are occasional moments in skyrim where you look up at a mountain with the aurora behind it and a dragon silhouetted against the sky and you say "That's awesome", but...ultimately, it's just not good enough to be all that different. Sure, the plants look a little bit better; sure, the mountains look decent, but that's all they are; decent. You might not notice it at first, but then you look closer and realize that yeah, the rocks still aren't that well modeled, yeah, the leaves are just 2-d images, and then you walk through them and nothing happens, and the illusion breaks completely. For me, Skyrim sits on the uncanny valley, while Oblivion rests just outside and below it. Not terribly realistic, but this is a FANTASY game, I'm not expecting absolute realism...at least, not yet.
Another thing that bothers me is how people exaggerate how great the dragons are. "They provide an entirely different experience!" they say. But they don't, not really. Sure, they show up out of nowhere, swoop down and take that guard off to kingdom come, but you can see in every moment of that swoop just how scripted it was. You might not notice it at first, maybe not even in your first 50 dragons, but after a while you're going to realize exactly what you can do to manipulate the AI, and suddenly they stop being exciting and start being a chore. A big, flying chore, that follows you all across skyrim and doesn't really do anything for you after you get all the shouts you use, leaving you with the annoying choice of whether to keep your RP up and waste 15 minutes killing a dragon that has no possible reward for the doing so, or remembering that this is a game and you can just go into a house and out again and the dragon will be gone in a poof of logic.
Here; I'll show you. The dragon's patterns.
1: Fly around breathing fire or ice on things.
2: Land and breathe fire or ice on things.(or BITE! ooooooooh)
3: Grab an NPC and shake them around.
Seriously, that's IT. Oh sure, you have that standard crash animation, but after you see exactly the same one for the 20th time it kinda gets dull.
Of course, you could counter me by saying that it's just a game, and they only have so much time to program something like this, to which I'll reply, "Seriously? It's practically the reason most people buy this game and they don't have the time to put a decent amount of effort into it?"
Yeah, a decent amount of effort. It just follows that mind-numbing tradition of SAMENESS that skyrim is infected so deeply with.
Sameness(if it's not a word, it is now), is probably the biggest problem Skyrim has. I already pointed out the dragon one; all dragons act pretty much the same way, and every dragon fight is the same. Find cover, pelt the dragon with arrows, wait till it lands, either A

elt with more arrows till it dies or B:run up to it and click as fast as you can until it's dead.
Enemies don't get any more interesting, they just get more and more health. Never do you run into an enemy that has, say, 99% resistance to physical damage and 50 health. Never do you run into an enemy that has the same thing except with magical resistance. And those are TINY examples! Things that could have been done SO easily that I thought of them in literally seconds before my thoughts finished transitioning into what I'm typing here!
And then scaling. The thing about scaling is it allows you to re-use the same dungeon over and over. But I don't WANT to re-use the same dungeon over and over. My streamer friend got into the problem of extreme boredom because he knew EXACTLY what to expect from every dungeon he ran into, and was skilled enough to kill EVERYTHING, even on Master++(modded) difficulty! There should be times where you HAVE GOT to run, because the world doesn't revolve around you! That's one of the reasons why I adore OOO from oblivion so very much; in the very beginning, across the lake, there's a ruin you see just as you leave the tutorial dungeon. In OOO, if you enter there, first you get massacred by bandits that are just hanging out outside it. Then, if you manage to kill them, and are feeling pretty badass for doing that, you go inside and promptly get curbstomped by ayleid spirits. It's the ultimate in lessons on dealing with a harder game, but it immerses you in that world like nothing else does!
THAT is what Skyrim is lacking. It might have fancy graphics and features that look great on paper, but ultimately it's an ill-fitting puzzle, with pieces missing and some pieces from other puzzles shoved in where they shouldn't be, leaving you just enough to get an idea what the amazing original idea should have looked like, but leaving you with a sour taste in your mouth to ruin all that before it gets rooted.