Among the best RPGs of all time -- quest design, storyline, characters, combat all hit high marks.
Some of the quests are honest-to-goodness *funny* -- discovering a ghost town devoid of life, only to find out the whole town was turned invisible by a rogue mage nearby. Or saving an Orc Noble's daughter from abduction and getting to hear the Orc Nobleman pathetically attempt to speak like a sophisticate to you, only he sounds like Don King inventing hilarious bogus fancy words to hype up a boxing match. I've barely made a dent in the overall quests here, and I can't wait to see more.
The other accomplishment worth mentioning is how good the combat design is. I'm playing a melee warrior type, and there's true technique demanded for fights. Block-and-jab, darting in and out of your opponent's range, opening the fights with poisoned arrows from distance and closing for the kill, managing your buffs and potion effects. Different monsters require different melee tactics, which feels very cool in-game and realistic. A heated fight really makes you feel like you're in danger, using your surroundings for cover if needed, and using blocks as often as attacks. Overall, the combat is leaps and bounds more interactive and rewarding than what you saw in Morrowind.
All the other good points are covered in other reviews -- I just wanted to sign praises of the combat and quest design, which are truly phenomenal and any fan of true RPGs will appreciate.