It's not my favorite game by far, but I've enjoyed Skyrim a lot, and it holds a personal distinction for me over Morrowind and Oblivion as a TES game I will likely actually finish the main quest for, rather than trail off playing out of boredom with wandering around (Morrowind I got hopelessly lost in at one point and just gave up). I realize with any TES game YMMV and if you liked these earlier games, I'm glad you did. I just got frustrated. (As an aside, I've also noticed that with every TES game that comes out, it always seems like there's a wave of "THIS is the BEST TES game EVER" followed by a bunch of people who decide the oldskool is better after all. I wish y'all'd make up your minds.)
Anyway, Skyrim to me is more interesting to wander around in, it's less easy to get lost, and there's just enough variation in what you run into to never feel like I'm just kind of standing around picking my nose. I do like most of the quest storylines (with some exceptions like the hideous railroad that was Markath's plotline). Unlike Morrowind and Oblivion, there are NPCs whose names I actually remember because they were interesting enough to remember.
That said, there's a lot that could be improved (I have yet to explore mods), and in the vein of the OP, "All Skyrim needs is..." ...
- Skills need to develop consistently at similar rates. It's easy to build up my weapon skills--just keep using it. Any weapon will do in the right category. But to smith, not only do I not need to keep smithing, I've got to find materials and I've got to find the workshops and I've got to take the time to smith 8,000,000 warhammers and whatnot in order to level. AND I need to keep crafting increasingly more valuable stuff to continue to get the fastest leveling out of it (no more iron dagger exploit). Out of sheer desire to make use of all the damned dragon scales and bones I leveled the whole damn smithing tree and I think I wasted about six hours of in game time doing so. And I don't even think it was worth it, save to have a nice matching armor set. Ah well, next playthrough I'll ignore it, but it's annoying still.
- A better mechanic that triggers NPC reactions and at the right time. I had a woman persistently asking me to clear the creatures out of her mines while a dragon was literally trying to set her on fire. However they code NPC priorities to react to you versus their surroundings needs to be done much more carefully. (This is especially frustrating because often the most epic stuff I've seen in Skyrim has been totally random AI incidents, like a dragon versus bear fight I witness that was strangely epic.)
- Related to this but more specifically, there needs to be far fewer barkstrings. People do not need to say the same damn "Do you know what's wrong with Skyrim these days? Everyone's obsessed with death," every time I walk past them. People can nod or say hello to you, but they shouldn't say anything to you unless you trigger talking to them or they are approaching you for a quest. This dramatically reduces immersion rather than the opposite.
- There should be a reputation system (a la Fallout New Vegas) instead of people just checking basic faction allegiance and/or skills. If I'm the head of the Dark Brotherhood, head of the Thieves Guild, head of the Mage's Guild, head of the Companions, and Thane of every major region in Skyrim, people will have heard of me one way or another. They will not trash talk me for being the Companions' "mead carrier." They will not demand 100 gold in tolls. They will not tell me to stop lollygagging about. Because they know I could bring half of Skyrim, if not more, on top of their heads. In fact, as you build a reputation, Jarls and such should actually grow wary of you. Realistically, you become an extraordinarily politically powerful character in addition to just a physically/magically powerful character, and yet the game consistently treats you as an unknown. Even quests do this -- if I'm the well-known Dovahkin who just negotiated a truce between the Empire and the Stormcloaks, you want ME to be the one who goes undercover to the Emperor's feast pretending to be a chef? You're a moron. Maybe more that's it--if you're granted political positions in the realm, you should be able to use them to affect politics, and save for very specific scripted moments, you can't. Again, immersion breaker. Don't give us the titles of power of they are ultimately meaningless and every guard is still mocking you for carrying mead.
- A way to say to all non-essential quests, "I am not going to do this," so that it will be removed from your list of quests. There are several optional quests that you cannot remove without using the PC debug console (the worst offender is the Paarthunax quest, which you do not have to complete--and in fact in many ways are at an advantage if you do not--but it will not resolve and remain your quest list unless you do the kill you are asked to do. You can even say to the quest givers that you refuse to do the kill, but the quest won't go away. You can't even force-fail the quest by killing the quest givers because they're marked as essential. *wallbang*). ETA: Actually, I think I lied, the worst offender is the Civil War issue--if you decide to avoid joining either the Stormcloaks or Imperials, you can never talk to Tullius or Ulfric because they will force you into a conversation that basically forces you to say you want to join their side, and you otherwise can never converse with them until the quest is "resolved" (which if you don't want to follow it, you can't resolve it).
- Fewer rabid animals. Wolves and bears are not going to persistently attack you when there is easier game nearby unless you're actively threatening their territory/food. They are also likely to run away when in one blow you've practically severed their leg off. Bears are more aggressive and persistent than dragons. Seriously, I have had a bear chase me across half of Skyrim while dragons avoided me like the plague. What is wrong with this picture?
- About 1/4 the companions and marriage candidates, or even fewer than that, and the ones remaining need to have real dialogue that changes and advances as the storyline continues. What's the point of having a billion possible companions if ability and conversation wise they are largely interchangeable?
And what's the point of having spouses if all you ever get to say to them is "give me food and money, *****"? If I wanted to do that I'd get married in real life.
I know Bethesda is the world building company and not the script writing company, but if they're going to go the route of giving folks romances and companions, then they need to do it right and make it meaningful, or not bother at all.