This game is great for people who like RPGs.
It has lots of open world content with quests, caves, treasure chests, world bosses, and non-instanced dungeons.
It also has really difficult instanced group dungeons and trials (raids) if you're into that kind of thing. But by no means is instanced content mandatory in the game.
ESO also has some of the most fun PvP I've ever seen in an MMO. You can queue for random battlegrounds once a day to get bonus xp. It's a nice diversion of you're tired of trying to complete zones.
What really sets this game apart from competitors is the massive amount of non-repetitive content in the game. I would recommend it to anyone who likes open-world RPGs.