As we all know, the game is awesome, not perfect but better than any other game. TESO was huge success at launch and game was exactly what everyone wanted. I am going to list few reasons why the game is better than any other MMO on the market at the moment.
When you log in for the first time, the Elder Scroll "feel" hits you with full power right away. The beginning is just like in other ES titles too and even if you painted different skins to NPC's, you would know it is an Elder Scrolls game.
The game looks like Elder Scroll, the game feels like Elder Scroll, the game tastes like Elder Scroll, the game smells like Elder Scroll, the game is definitely an Elder Scroll, but online.
The game is so different from all other MMO's that are just clones from each other. If you have played any MMO before, you have played them all, except this one.
There is no autoattack like in all other MMO's. You actually have to hit the enemy yourself and you have to block hits yourself just like in other ES games. Combat is generic elder scroll combat without cooldowns and you have to manage stamina and magicka resources, just like in other ES games.
We have full voiced NPC's with race specific voices just like in other ES games too and story is as good as in other ES titles.
When you start a quest it will be about a myth that you have solve, you end up in an ice cave where you have to save a frozen man. This is exactly what you would expect from ES title when in every other MMO all your quests are: "kill 3 wolves"
Everyone can use any kind of weapon and any kind of armor they wan't, just like in other ES games. You can mix heavy and light together if you feel like it. Mage can switch to tanking if he feels like it and that is not possible in other MMO's but it is possible in other ES games. Usually in other MMO's you get to wear one type of armor, in the best case, few different weapon types, usually only one.
The game starts when you log in for the first time, not when you are max level. This is not the way in other MMO's but it is the way of other ES games.
Vampires and werewolves, nuff said about them, they are awesome as they should be since this is ES-title.
These are the reasons for the huge success the game has achieved. I am sure there are a lot more reasons but these I just conjured from my head in few minutes. I am going to go back to play now, cya.