The Good:
I loved the improved character interactions. I loved having actual companions who went with you on adventures. I loved it even more when Dawnguard was released and Serana was introduced. Her programming was obviously an even better version of the better version we had in November 2011. I hope this is a trend for Bethesda and that the NPC's will become even more rich and interactive in the future.
As an Xbox 360 console player, I love the Kinnect shouts and commands. Being able to verbally change my spells and weapons was a big improvement over the rather clunky menu/hot button favorites we started with. The shouts work better in English because you don't have to time your trigger pull with the Nord language, but I'll bet that Kinnect commands will be even better next time.
I loved the improvement in the Bosmers; their looks, their voices, etc. In Oblivion, they were a joke. In Skyrim, they were fun to play.
I loved the world Bethesda created. It is painfully cold and sometimes bleak, but it is also breathtakingly beautiful at times. It isn't as pretty as Oblivion but it is much more spectacular! The first time I saw the Ice Fields in the far north with the aurora borealis in the sky--I was blown away! It felt EPIC then and still does.
I loved the soundtrack. It still haunts me a year later. Beautiful music.
With some exceptions to be noted below, I loved the questlines. Oblivion could be a "Mary Sue" joyride at times. The quests in Skyrim seemed much more serious, and important, and they had depth. There were also some shocking suprises.
I enjoyed having a DLC that had more to do with creating and caring for a family than killing and looting. Thank you, Bethesda for Hearthfire. It gives me a nice sense of accomplishment to build a home and move my family into it.
The Bad:
It was a mistake to force players to join factions in order to complete the MQ. It was a mistake to force players to join factions in order to complete certain important shouts. It was a mistake to tie some Daedric quests into important questlines like the Thieve's Guild. It breaks immersion to have to join the College to complete the Guldar amulet, or finish the MQ (I know, you are supposed to be able to say "I'm the Dragonborn" but that option has not been available to my characters since the DLC.)
It was a mistake not to have a marriageable option both male and female for each race in Skyrim. Imagine my Bosmer's disappointment to discover that there wasn't a single available Bosmer male in all of Skyrim to marry. I am certain others felt the same way. It was also a mistake to have the the only Breton female be available for marriage only after you do a DB quest and kill for her. What was that about? Please give us sane marriage partners for each race in Skyrim and please don't make us have to become assassins to please them. My Bosmer sighs unhappily each and every time she enters The Drunken Huntsman and knows that she cannot marry either of the brothers.
I miss the simple elegance of spell-casting in Oblivion. Skyrim's spells take forever to charge and often won't go off at all if you are backed into a wall. It make no sense that I cannot cast a spell with my left hand while holding my bow in my right hand or vice versa. I understand that it has to do with programming and dual casting, but it still doesn't make sense and it annoys.
The Ugly:
If I have to play ring-around-the-mountain one more time in search of the path to my next quest, I will scream. Oh, heck, I've already screamed! A lot! The single most frustrating thing for me in Skyrim is trying to find the path to my next quest! Please, please, please give us better road maps next time... please. The endless search for the path is an ongoing source of frustration for me as I play this game.
Glitch, twitch, glitch again. Some of the bugs are funny, some are sad. But some of them are quest-breakers. Please fix the Companions questline. I really would like to heal Farkas or Vilkas at least once before I die. I am certain that others probably have similar bugged questlines that are a constant source of frustration.
Why, oh why, did you not give me the chance to decimate the Thieve's Guild? Surely you considered this epic quest, right? In fact, it sounds like a DLC to me!
Well, that's all I can think of at the moment. Love the game, thanks for creating it.