How have they aged? I started with Morrowind, so was never able to go back and play Arena/Daggerfall. Are they worth re-visiting? Or playing through for the first time?

I tried Daggerfall about 10 years ago.

It made me throw up. Literally. Motion sickness.

So if you're prone to motion sickness in old first-person games, you might want to wait until somebody else confirms whether the emulation here is the regular, vomit-inducing DOSbox emulation. Which it likely is :(

That is concerning to hear! I've never had an issue with motion sickness and video games, but it is certainly good to be aware of!

No matter at how many CPU cycles DOSBox runs both games have an appalling frame rate at times, which might lead to motion sickness.

Since Arena and Daggerfall haven't aged particularly well, this might be a project worth taking a look at:
http://www.dfworkshop.net/daggerfall-tools-for-unity/

Well, that depends. Gameplay-wise they both are a lot more interesting than Oblivion and Skyrim (haven't played TES Online), probably among the best role-playing experiences you can find in the single-player world.
Graphically, they are definitely not on par with today's games (although especially Arena does look quite nice in my eyes).
And they are a lot more difficult than the later TES games. A LOT! Don't expect these games to hold your hand, like giving you quest markers and presenting only defeatable monsters to you.

Here's a series of articles about an Arena LP. It's one way to see if you want to play it. http://www.shamusyoung.com/twentysidedtale/?p=28081

Didn't like Arena. Daggerfall is close to a masterpiece - the factions plays out extremely well in Daggerfall.

I agree with Azghouls. Arena can be ultra-hardcore. I tried it several times and only once got out of the first dungeon. Daggerfall however is a lot like Arena, but a lot better in most regards. It takes some time getting used to, but then it's really fun.

Daggerfall could have been the best in the Elder Scrolls series. I still play it from time to time. The faction play is very complex, character customisation is much greater than in any other elder scroll game, the map is HUGE and the atmosphere is great.

Unfortunately the graphics don't aged well, the controls are clunky at best and there are many bugs, some of them gamebreaking. Also the ramdomly generated dungeons can become a pain in the ass because of there layout.

If you can stand the old graphics an if you have patience you should try daggerfall.

Arena is in my opinion the same just with less features than daggerfall.

What do you mean "aged well"? They're exactly the same games they were back then. Games don't age, only people do.

I should probably point out that the games are still buggy. Daggerfall was so bad that they got all the way up to version number 2.1.3 and *still* hadn't fixed all the bugs.

Just remember to save early, often and in multiple slots in case something goes wrong.

Of course, this applies to all other games developed by Bethesda. (I hear Skyrim wasn't as bad, provided you didn't happen to get your hands on version 1.2, but you should still be careful.)

Arena never ran right form me, but I never had problems with Daggerfall in DosBox. I replay it once every now and then, have never finished it because the random dungeons can get you lost for hours if you can't find the objectives (mark and recall spells are a must).

Disagree!

- I never had any problems with Arena.

- As far as I'm concerned, there is only one problem left in Daggerfall 2.1.3: You can still fall into the void occasionally. But 2.1.3 contains a workaround, which I can live with (a certain parameter setting, which let's you "return from the void", if you press a certain key). No reason to call 2.1.3 "buggy", in my mind.

- Morrowind and Oblivion had a few problems initially, but these were fixed over time. The current versions don't have any major bugs (as far as I know - maybe they are hiding well on my PC).

- I didn't play Skyrim from the beginning. When I started, I didn't find any problems.

I know from my own experience that it's not pleasant to play a game having serious bugs, and it's ok to complain, but generaiizations (like "Daggerfall is buggy" or "this applies to all games developed by Bethesda") are almost always wrong. Don't get me wrong: to save regularly and to keep several saves is generally a good idea, not only for Bethesda games - now I have generalized myself :-)!