In my opinion, ESO is going to be far better than any other MMO on the current market for one simple reason: It's going back to the good old days of game design. As an ex-SWG player, and someone who has played just about every MMO that's been released since SWG crashed, I've seen a steady trend of MMO design going from absolute freedom to the most inane restrictions you can imagine. We went from vast, open worlds with player-driven content to tiny cramped themeparks run by overly strict AI dungeonmasters. We went from games focused on socialization and interacting with people to games where you practically solo everything until you hop into a warzone/battleground queue or go into a dungeon or instance. We've gone from having an overabundance of roleplaying and socialization tools to a point where most games wont even let you do something as simple as sit in a chair at your local tavern or cantina.
The industry has constantly and consistently dumbed down MMO mechanics, implemented more and more restrictions, and at the same time begun to find new and interesting ways to charge people money for the simplest of features.
From what I can see, ESO is doing a lot to alleviate those concerns with the modern mmo market. It will be pay to play, which us old time MMO'ers are used to - Personally I hate the microtransaction system that everyone else uses nowdays, because it always ends up costing you more in the long run, especially when you're having to pay a subscription on top of it just to be able to use the basic features of the game. ESO will forfeit the idea of instanced battlegrounds and warzones in favor of open world pvp, giving a great deal more freedom to players in how they approach their enemy and how rewarded they feel from engaging in pvp combat. It will loosen up the class system and almost reaches the level of character customization we saw in starwars galaxies, where you can pretty much make any combination of any skills or weapons you want.
At the same time, it looks as if ESO is taking the few good things that newer MMO's have presented us with and implements those as well - voice actors, an engaging storyline, customizable appearances, so on and so forth.
I havent played beta yet, so I'm going off of reviews and videos and news releases here, but if the developers at zenimax can pull off what they claim to be pulling off, this MMO will be absolutely perfect for both veteran MMO players and new gamers alike.