Skyrim had big shoes to fill, Oblivion was a really great game in a lot of aspects. In all aspects, it trumps the old and even brings newer things up to par with what's expected.
The combat system requires a lot more consideration, you can't just stand there and laugh as you could sometimes in Oblivion. In this game, they made sure that you were kept on your toes with enemies. The addition of a dual-wield is beneficial, and the shield is now able to be effective. The perk system is much better than the old Oblivion leveling system, and a lot of benefits lie in even the lower echelons of each skill tree. There's a lot to do, and while a fair amount of it can seem repetitious there's always something new to make it seem different.
A lot of the annoyances of Oblivion skills are removed, it's far more streamlined and more effective. You can level up and take new perks when you want, not just when you sleep anymore. Anything you choose, you don't have to worry about strength being terrible or magic abilities to be overly deficient from base stats. The Shouts are really fun as well, and keep the game really entertaining and helps with any build of character. The amount of different voices is far larger than that of the original game, practically the only time you run into an old voice that does sound familiar is the enemies. Enemies are smarter than they were before, but they can and will make stupid decisions. Your Followers are no exception, but they're actually brighter than most enemies you run across. They can be a major help in situations.
The lines are better than they were in Oblivion, though some are remarkably...Odd or stupid. And some questlines seem to end with your being made the leader of a guild, which can be a bit annoying with how quickly they seem to trust you. And now, with the bad entirely. Textures can be fairly off, ranging from really good to fairly bad. It can really glare at you, how bad they seem to get at times. Glitches aren't common, but there are some times where it's a bit frustrating. The game also freezes at times on my system.
However, the faults rarely take away enough to make the game unplayable. In fact, the game is extremely entertaining a lot of the time. I've lost hours straight playing, and almost never felt a bit of boredom. 9/10