The differences between the games are:
Nothing! The end.
Ha, just kidding. I was very surprised, at first, with how similar the two games are in terms of gameplay functionality, feel, and exploration. Actually, “similar” is not the right word… Those things are exactly the same! Even the engine doesn’t feel any different, and the graphics are on a very similar level.
For both games, I have completed the main story quests (and made a dent in the side quests). So, I’ve gotten to see and understand the bulk of the two. I decided the main difference is… The dragons. Obviously. Skyrim is really the first game to have dragon slaying like this. There may have been dragons in other games, but not like this. The dragon interacts with the world, and you can use any means imaginable to kill it. It’s too bad the dragon fighting is terrible though. It may have been a very ambitious attempt, but Bethesda has a long way to go with it.
The only other major difference is in the combat. The dual weilding concept is a unique idea and fits like a glove on to the role-playing, item-collecting, skill-building style.
There really aren’t as many differences as you might expect to find in an anticipated follow-up. But I guess Bethesda isn’t fixing anything because NOTHING IS BROKEN. They make the perfect fantasy rpg.