As previously stated, the games are Free to download. You don't have to buy them.
Arena...
Combat+Controls - Unfortunately, there's no way I've found to re-bind the archaic keyboard commands, making getting used to the game difficult, and at best it's still slower and harder than the new ones.
Roleplaying - You're stuck in a predetermined, extremely limited class, instead of the free choice in later games.
World Design - Every city and main dungeon is its own world-space in an infinite-scrolling area. The only . There are no guilds. Most quests are just running around town, but you might get an artifact quest. There are a few dungeons outside of the towns. Areas other than the main quest dungeons are level-scaled.
Lifespan - It seems to be a novelty nowadays, but Daggerfall is an improvement in every way.
Setting - All of Tamriel, via the magic of Copy+Paste and Palette Swaps!
Daggerfall:
One advantage Daggerfall's combat has over Morrowind's is that you don't need to hit the target with the attack AND deal with miss chance - if you're in range and can see the enemy, you have a chance to smack him, making archery pretty fun. It's possible to "parry" attacks by swinging at the same time as the enemy. There are no other active defenses, and Block isn't a skill - Shields just increase locational armor class. There are lots of weapon skills to choose from, but Long Blade is best of the melee weapons. Short blades are decent because you can start with an Ebony Dagger. Axes are neglected. Hand To Hand is surprisingly useful, though - It bypasses all immunities from the start, so you don't need to make sure you're using the right material. You can sort of "Dual-Wield", but not really - you can equip a weapon in each hand, and swap between them with a button press. It has very few niche uses, though - such as possibly having a high-damaging inferior-material weapon in one hand, and low-damage superior material in the other (Such as a Steel Katana and . However, Hand-to-Hand and Archery complement each other well, because you always have Hand-to-hand available as the "off-hand" when shooting a bow. On that note - actually switching weapons (instead of switching hands) takes a long time, making it impractical to switch between, say, a bow and any other weapon. Also, the keys are completely remappable, so you can make it function similar to later games in the series.
Roleplaying - Depends how much you can suspend your disbelief around the random generation of things, but it's pretty strong. The main quest is the best in the series for player agency and decision-making, but the dungeon crawls can be tedious - especially main-quest dungeons. Unfortunately, the game is very shallow, though stunningly wide. Unfortunately, this game has the worst case of psychic guards in the entire series - it's impossible to commit a crime without getting their attention. Fortunately, avoiding fines and bounties amounts to avoiding getting hurt while being pursued. Unfortunately, that means you get a fine if you get hurt from falling damage by misjudging a jump trying to run from the guards.
For some reason, though, the high courts of the Illiac Bay are perfectly fine with a naked catgirl barging in and expecting to get an audience with the - reactions based on clothing was one of the millions of ideas left on the cutting room floor, along with prostitution, dynamic warfare, A mage's guild knightly order (Cut because it gave non-magic users too much access to wizard stuff), and all sorts of other goodies. This game was Peter Molyneux-level ambitious or more.
I think Mikedzines summed everything else up perfectly.