This is mainly from a game engine (or graphic engine, whatever you call it) perspective.
I have played a LOT of moms, from EQ to WoW, SWTOR to Rift, Warhammer Online to Wildstar. You name it and I have probably played it. But what I have never seen, is an MMO that is so smooth, so fluid and so polished than ESO. Everything from moving around the world, to the UI, to combat, it's all incredibly polished.
Other MMOS I have played, there is jank, whether that is from a minor stutter when opening a game window, such as Achievements or your World Map, to huge performance issues from just standing in an empty area, and your FPS just plummeting. ESO has none of this, and even though it may not be THE MMO that I spend most of my time in, I just wanted to give my huge regards to the developers for making such a clean and polished MMO. It's not easy and they deserve all the credit.
I know this thread is about to get high jacked from those who don't agree with me, and think the engine is the worst thing in existence. I have a fairly powerful machine which helps, but I think the above mostly still applies, regardless of your machine, providing you meet recommend specs.
So thank you devs, for showing every one that you can have an MMO with a clean, stutter free UI, and gameplay that feels just as fluid and polished