Well, if you like themepark MMOs, ESO is a fairly solid offering. I don't know if you are more into PvP or PvE, but ESO not only offers both, but allows you really to deal with playing how you want (not really forcing you into a build or role, or even into a play system.) The freedom to define your character by what you do is nice, and the class skills make little impact to being able to do anything with a severe bonus as compared to anyone who is not that class.
As with any MMO, the people are the biggest deal going for it... and GSCH is always a fun group.
If you like well written quests, ESO has above average writing. It has a lot of immersion factor played in default mode, but plenty of mods for giving you more information if you want. There is a fair bit of content, especially if you enjoy quests, as any character can go through all three faction storylines.
It has a much more classic themepark feeling to it at times than GW2, but is definitely a hybrid action MMO with rewards for playing well.
The justice system is shaping up, and looks like it may be very interesting to deal with once players become a key part of the equation beyond just you yourself and those who open a strongbox before you get there. *There are many things on the plate for the game, from that to housing to spellcrafting to the dark brotherhood and beyond. The team had previously slated many of those things for late this year or early next... but there is no guarantee for any of them.*
Honestly, it is an MMO. If you want a reason to play it, that reason must be because you want to. If that is missing, then there is no reason for you to play the game. If you want to experience it a little, I agree with Eiahn. Go watch a video or three before picking it up.