You're a WoW vet if i remember right, so there are a few differences like a more active combat system that makes use of dodging and blocking depending on what weapon you have and your class, but significantly less skills overall. Only 5 per weapon.
Aside from the main questline, the rest of the game is based around dynamic events that happen around you and that you can participate in, with the result of the event leaving some sort of impact on the game world e.g. a village being conquered by centaurs and thus effecting local trade.
Graphically it's ahead of WoW, and the animations are a lot nicer, but then WoW is from the early 00s and GW2 came out in 2012. I think you'll appreciate the game world a bit more, and there is an emphasis placed on exploration through Points Of Interest and Vista achievements.