Skyrim was the first Bethesda game I feel is totally playable and fun to play more than 50+ hours without mods. I put 100 hours on just one character alone, and I didn't start adding real mods to it until 80 hours in, which is way more than past games.
There are some serious issues, and Bethesda really suffers from developing in a bubble and never focus testing (they even said this themselves) which means obvious design issues get passed as final, but the game as a whole is enjoyable from the start. It fixed every issue I had with Oblivion, though it introduced new (less severe but still bad) issues. Such as questing being awful (which is doubly so when the entire game's design focuses on questing over the actual world unlike Morrowind), and a lot of the RPG design was very poorly done. But these are things that didn't outright make me go "... really?", they were just lackluster and uninspiring compaired to everything else, and they are things that are theoretically able to be fixed with mods.
This is why I can't wait for the expansions, because hopefully they will have learned from their mistakes in Skyrim and make the new quests amazing.
The RPG stuff can possibly be fixed too but I'm not holding my breath.