at least GW1 has a kind of consistency so everyone could play on a stable but fun way, GW2 is good in it's own way but it encourages grind and farming allot more and allot of things are out of control.
i have had more crashes with GW2 in one month then i had with GW1 in 4 years, the game is simply not stable enough and it misses something that made GW1 so good.
to answer your question, GW1 had the flexibility to go from one place to the other, follow the story line you want to follow and have no restrictions on replaying a part of a story.
GW2 forces you to pay just to get somewhere which is getting more and more expensive, the story lines are locked behind your personal story and you can never ever play a different path ones you choose one.
it is missing some more things but that just takes to long to go in to, the point is just that GW2 can use some GW1 spirit in it.
let us play a mission in an instance just like in GW1, let us choose a different path ones you completed the story to a part and let us get what we want even if it's not part of the story you chose.