GW2 is a very Skinnerian game... it relies heavily on the incentive structures that are theorized to make games fun, and that's its greatest strength by a wide margin.
Actually, I think where GW2 excels most is being a very polished game with a more action-oriented battle system and different styles of quests. At first, it feels very new and different.
I think one of the bigger weaknesses of GW2 is its incentive structure. Basically, there are no meaningful incentives for non-hardcore players... and from what I understand, there aren't many worthwhile incentives for hardcore players, either.
The essence of Guild Wars 2 can be summarized by reaching "vistas" in the game (for those who don't play GW2, the developers place vista points throughout the game, and you must reach these in order to "complete" different maps). Anyway, you go through all this trouble to reach the vista, at which point you're given a cool, pulling-back cutscene of the area you're in. It's pretty and all, but in the end, your character doesn't benefit from reaching the vista, and the entire activity is over in a matter of minutes.
FFXIV, on the other hand, offered things like the Materia system, which gives players much more meaningful, lasting goals to work toward over time. All the gamers I know consider that a strength of FFXIV, whereas the incentives/character progression of GW2 was kind of a joke. Edited, Feb 22nd 2013 11:40pm by Thayos