Ok right now I only own Nightfall, and I must say Nightfall has made me reclaim a love for Guildwars.
I started with Prophecies when it first came out, quit prophecies, started replaying it before factions came out, quit it again because the fragmented story and the fact that I had no idea what I was doing made it kind of a bad experience
I bought Nightfall about a month ago, Started off as a Dervish (got it to 20 finished 10 missions) then made a Paragon (two missions left) and I must say this has been the most fun experience in an MMORPG I have had because the mix of Story, the million different ways to run a build, and being that my Alliance is awesome with people that help me and not criticize me when I have a question.
So now I am almost done with Nightfalls, and I will start doing the elite missions soon, I am looking into seeing what is the next Campaign I should buy. Prophecies, Factions, or GWEN
I am asking for your guys opinion and here is my Criteria
1) Storyline
2) High End Content
3) Amount of time needed to Game
Help me figure out which I should buy next
X

also got the most content for your money and possibly the cheapest of the three main installments