In my opinion, if you laid all the maps of all the different zones out side by side in to one large map, EQ2's overall map size would be about 2x to 3x as large as WoW's. Now keep in mind, I haven't logged in to WoW in a couple of years so they may have added many more land masses since then. On the other hand, so has EQ2.
As for FFXI.. no clue. I have only played it briefly here and there to hook up with friends that play during live events.