Daggerfall vs Morrowind
I've played both Daggerafll and Morrowind. Both had similar strengths and weaknesses. Large worlds, interestign game mechanics, highly customizeble characters and magic/enchantment systems, lots of interesting sidequests that could easily keep a player entertained for weeks...and awful main quests that weren't nearly as fun as the rest of the game.
Daggerfall's main quest was arguably better written than Morrowind's. I don't recall ever staring at the screen in shock at how stupid it was. I did occassionally do that while playing Morrowind. But Morrowind's main plot was far more interesting overall, however head-on-desk-banging stupid it was at some points.
Morrowind suffered from a slight lack of replayability compred to Daggerfall. Daggerfall had a lot of dynamically generated content. And some of that content was comparable in complexity to some of Morrowind's guild questlines, and with less railroading. Daggerfall's quest had far more flexlibilty in how they were completed, and with multiple possible endings. But, Daggerfall's dynamic content while sometimes very good, was sometimes irrelevant for how similar things were. Some of the random-joe-nobody-in-a-tavern questgivers spawned quests that were far more interesting than some of the guild quests, some of which were notoriously bad. Mage guild kill quests, for example, were amongst the most tedious affairs in the history of gaming.
...which brings us to Daggerfall's dungeons. Daggerfall had dungeons bigger than most games. Completely and entirely literally...you could go to a random crypt of no consequences in the middle of nowhere, and sometimes it would be a 4-hour long affair. And not because of combat, but because the things were so huge. Individual Daggerfall dungeons were like 3-4 levels of Descent combined. Morrowind dungeons were generally entirely liner affairs. Go in one end, maybe make one or two redundant choices, possibly follow a circle, then reach the end turn around and go back. Daggerfall dungeons were labyrinthine extremely three dimensional mazes, and some individual dungeons (Castle Necromoghan comes to mind) were quite possibly bigger than every dungeon in the entirety of Morrowind combined.
Impressive. But...honestly Daggerfall's dungeons went beyond what could possibly be considered fun. They were too much. And their 3d layout was so honeycombed and complicated that sometimes even something s simple as navigating an inch up on the map visualizer involved several minutes of zooming and rotating to find a path.
Daggerfall also failed in its world map. Yes, it was notoriously big, possibly the largest computer generated game world ever made, without thousands of cities and dungeons and an overland map that would probably takes days or weeks of real time to traverse. In fact, it was so big that most players didn't even realize it was possible to travel from one town to another without automated fast travel. But...there wasn't really much reason to because it was all the same. And there wasn't much reason to visit any of those thousands of cities and dungeons because they were also all the same. And with the way quests were dynamically created, there wasn't really much reason to go anywhere at all. You could easily pick one city with each of the various guilds you cared about and spawn random quests all day long and never have to leave. In fact, as large as many cities were, that was kind of the only reasonable way to play. A medium-sized town in Daggerfall might have several hundred buildings, and spaced out enough that even with magically enchanted speed and flying it could take a couple minutes to travel from one end to another. Larger towns tended to take so long just to get from point A to point B that it was unpleasant. The capital in Daggerfall was big enough that flying from one end to another was a feat of similar magnitude as flying the entire overland gameworld in Morrowind. And it probably had more individual buildings than the whole of Morrowind, too. That's...one city.
Daggerfall did some things very much better than Morrowind: Daggerfall's character paper doll was better. It was pretty much a playfkiss doll game. Hundreds of different possible outfits with lots of cosmetic accessories. Morrowind did this as well, but Daggerfall's was better. Even individual shirts had multiple graphics sets so you could wear a shirt tucked in or loose. Daggerfall's quest generation was better than Morrowind's entirely static quest set. Daggerfall's spell and enchantment system was (debateable, but probably) a bit better too. But other things Morrowind did better. Alchemy in Morrowind was vastly better than the potion maker system in Daggerfall. Morrowind was prettier. Morrowind's world was more well fleshed out and full. Morrowind's dialogue system was much better. And some things they did about the same. Both had lots of ingame books to read. Both had optional quests that could keep one entertained for days or weeks.
Overall I'd say Daggerfall was bigger, more complicated in some ways, and vastly more ambitious. But Morrowind, while smaller, was more well refined. Morrowind was lacking in some ways, a bit simple at times, but overall it gave a better presentation, it was more "fun" and the world more memorable.
Finally, no discussion of Daggerfall would be complete without mentioning it's largest and most complete failling: It was broken. The game was so bug ridden that it was difficult to play to the end without running into some fatal problem that was irrecoverably destroy your savefile. To have any chance of playing you had to make regular backups, or at least cycle through the available saveslots. And sometimes even if you did you'd end up having to revert back hours of gameplay because irrecoverable crashes weren't immediately obvious. Daggerfall also had issues that would render the game unbeatable even without visibly breaking. The most obvious being that if you didn't meet one particular meeting deadline in the early game, it would become impossible to engage the main questline. It would be like in Morrowind, if you didn't report to Caius Cosades in Balmora within the first half hour of play...both he and all other relevant main quest npcs would vanish and it would be impossible to beat the game. And you wouldn't even know it.
Ultimately, I want to like Daggerfall more. It was a multi-level stone castle with a dungeon, moat and flying guards at a time when most other games were tents. But as impressive as it was, it was also unfinished. Tough to live in a castle when it's missing floors and chunks of loosely masonry occasionally fall from the ceiling on your head. Morrowind only seems small and simple in comparison to Daggerfall. It's still more open and more well developed than most other games of its genre. And it has enough refinements and improvements while retaining enough of the spirit of Daggerfall that regardless of the smaller scope, the fact is that Morrowind is more playable and more fun than Daggerfall. Morrowind was good. Daggerfall can best be summarized with "So, awesome! If only..."
So, Morrowind gets my vote.