So many people are speculating over Aion's supposed greatness but let us not forget another potential competitor in the MMO world. Star Wars The Old Republic, anyone who played KOTOR 1 and/or 2 knows what I am talking about. These were some seriously deep games as far as story and character growth and based on info, gameplay screens and videos SWTOR looks amazing and it is going to impliment a similar light/dark side growth method but far deeper than previous titles. Every decision made, every main person/npc killed will alter your path of good and evil and the "factions" opinion of you being friend or foe. I'm a FF fanboy but also a SW fanboy and personally I am keeping close watch on the development of both MMO's to see what I join next.
Played FFXI on and off since 03, recently came back but it still feels a little stale and repetitive.
Played WoW for a little over a year and can level to 80 and do endgame in my sleep, definately a stale game.
Playing XIV or SWTOR in 2010 but which? Time will tell.