I say questing in the single player games is better, not saying ESO quests is bad but you can easy get an questing burnout, doing quest to chill down is nice. In Skyrim you tended to do so much else too but in ESO its easy to get locked into one play style, has to grind to x, has to do pledges has to do quests in zones.
Now Fallout 4 managed to mess things up so quests in an MMO was good: Its an skill (sarcasm)
I definitely care about my choices in single player games where I can reload if I don't like the outcome, that's all the difference for me; it happened in ESO I gave the wrong answer even because I pushed the wrong button and being impossible to correct the mistake I started to NOT care.
That begun the day I threatened a harmless merchant because ZOS thought it was a splendid idea to put that answer first where usually the "sell" option is; impossible to undo, ideal walkthorugh ruined, stopped to care about quests outcome.
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QA's primary goal is tracking and resolving deficiencies prior to product release."
For an MMO I would say hands down ESO has the best quests. I think comparing an MMO's quest quality to single players is unfair as it is kind of like comparing apples to oranges in that MMO questing has different parameters they need to follow.
I don't think anything quite matches up to TES III: Morrowind's approach to questing.
"Quest markers? You don't need no stinking quest markers! You will listen to directions! And Tribunal forbid you miss the right turn down the foyada at the forked tree...or was that the left turn down the foyada with the forked tree. Does that even count as a forked tree? Well, looks like you'll be wandering in the ashlands for a while, Outlander!"
Questing in ESO. Questing in Oblivion is a close second. These two games have so many interesting quests. I don't like questing in Skyrim because it feels like most quests are just boring fetch quests and exploring Draugr and bandit filled caves. There are some interesting quests in Skyrim, but they're few and far between.
ESO's quests have a lot more NPC interaction, choices, and there are so msny different ones. Whether you're saving the students of the Aldmeri College, rescuing people from bandits, defeating daedra and cleansing an area or person of evil energy, helping former Argonian slaves get revenge on the family that worked their daughter to death, or just stealing a bottle of expensive wine there are just so many different quests that are much more fleshed out and make the world feel much more alive than other Elder Scrolls games.