I posted a lot of my wishlist in the What Skyrim Lacks thread so I won't rant too much but I can elaborate on one of the things i mentioned there:
I wish they had more adult kind of stuff. By that I do not mean a crass, vulgar outlet for stupid, horny 15-year-old boys to treat female NPCs like object of abuse & sexual assault because their life goals consist of growing up to be azzbrained, dysfunctional, misogynistic bottomfeeders who spew repulsive garbage on Reddit.
The gaming world has plenty of that. What I mean is, intelligent, savvy adult stuff for intelligent adults and intelligent soon-to-be-adults. We have a game that's full of fantasy violence, even fantasy taboo stuff like cannibalism and contract killings, but where is the ability to get fantasy drunk or fantasy stoned? Have a fantasy courtship prior to getting married, such as meeting together and giving gifts? Have fantasy sexual relationships with people who aren't your fantasy spouse? Get a fantasy divorce (we can pass on the fantasy lawyers)? Or have their fantasy spouse leave them if they cheat on them and are caught? Or hire a fantasy prostitute (and not just hetero female ones, thank you), and risk getting a fantasy STD? Or maybe have my character approached for fantasy prostitution? Or just have a fantasy fight with one of your NPC friends and you have go make fantasy amends to them? Or simply fantasy flirt with the fantasy mage mercenary at the fantasy inn?
I realize there's only so much that Skyrim can be like Second Life before it becomes Second Life with the Dovahkiin. But they created a world were you start relationships with people and then those relationships are a bit unsatisfying because they are static and don't develop the way we humans expect them to and we don't get to chance to make to kind of choices that make relationships dynamic. Hence why so many of us develop such extensive stories and imagine relationships for our characters that cannot be realized inside the game itself.
Also, you have a game where alcohol and illicit drugs are mentioned all over the place yet you can't partake of them is any satisfying, interactive way. I'd love to know why the Khajiit love moon sugar so much but when I eat it, I just turn green (or whatever) for a second. You even run into addicts--how about you being able to risk addiction, and then having to kick your habit. I mean, you can get vampirism and get cured of it, why not a skooma addiction? Or let me scandalize all of Riften with my indecent behavior after one too many tankards of Talen-Jei's Cliff Racers and then have to clean up my mess!
Like with the problem with Skyrim relationships being too static, so is your character's whole life there. They don't age and they don't really suffer consequences. At most they can go to prison for a spell--a prison from which I personally find a little too easy to escape (seriously, the guard unlock my gate and literally let me walk right out of the jail! ). Or they can die...and then respawn. So by adult stuff I mean choices-and-consequences kind of stuff that mold your character's relationships and bring more dynamics to your character's existence. That's all.