Factions was my first foray into GW too, and I have to admit it was the one that got me into loving and spending hours in the GW universe, eventually convincing me to buy all the other expansions and campaigns!
Personally, I loved the Asian feel and design of the entire place. Not only that, but as a Chinese person myself, it was just so enjoyable to see so much cultural design integrated into the whole of Factions. I think if Cantha could be brought back as some kind of paid for expansion (I expect it would cost a lot of money, time, and effort to add all of Cantha to GW2!) lots of people like myself would be thrilled!