Seconding Guild Wars 2! One of my favourite things about it is how when it comes to levelling, it supports whatever you want to do. If you literally just want to run around killing things and participating in dynamic events, you get experience for that. If you want to forego combat and just run around exploring the world and seeing what you can find, you get experience for that. If you want less freedom and would prefer a more structured story, guess what, you get experience for that. If you don't want combat or story, and instead would prefer to be a humble craftsman... yep, you get experience for that, too. (I accidentally leveled an alt to 80 just through crafting!)

The combat is a huge selling point for Guild Wars 2 in my opinion, as it spares you the dreaded 'hotbar bloat' of similar MMOs by keeping it simple. Every class/profession gets 5 main skills, 1 healing skill, 3 utility skills and an 'ultimate' skill. On top of that, a few of them may get a few extra buttons (e.g. for directing pets or swapping stances) but that's about it. Additionally, a lot of the content can be completed with any gear and more or less any build; you don't have to worry about minmaxing or being optimal if you don't want to.

Came here just write just that! got into Guild Wars 2 some months ago. The first part of the has cut-scenes, but the story is somewhat short. Once it is over you may repeat parts of it, but you can also ignore it.

I currently use it to turn off my brain, just roaming around the huge world, with full control on how intensive the game is. Do I work on some end-game mount ? do I roam high-level areas ? or do I just chill and jump between low-level areas ?

However, I don't listen to music while doing so, as the game's music creates a very nice atmosphere.