Hmm, I know about 60 people who've quit WoW, about half of those I knew before I started playing WoW, the rest I grouped with frequently.
And yes, WoW is growing, NEW people are coming into the game and many remain, I know.
World of Warcraft is a game that lures you in with instant gratification, then rewards you with endless grinds, it's when people get fed up with those grinds they either make a twink or tire and quit.
I have no doubt FFXI is even more of a grind, but at least I'm having more fun playing FFXI for whatever reason.
Blizzard did many things right, but the game is also too small and to make people at least do something they make us grind faction / gold. Yay, so fun... I've exped in I think almost every area of WoW, since I've taken multiple characters to 60 (it was fun for like 3 months after all), I'm still finding new spots in FFXI, I still have quests to do, and hell, I still have jobs I can level on my main character! omg class change without losing everything!
Heck, even Blizzard has admitted faction grinding was something poorly implemented at the last minute.
Now lets see, what can you do at 60 in wow:
Raid: this is cool if you're in the high end part, MC is boring...
Grind faction: this is not cool.
Grind gold to support raiding: this is cool, to a limit. Having to grind gold for Naxxramas access is ghey...
PvP: this is cool... but...
Wait in Battleground queues: 9 hours to enter Alterac Valley? wtf... 1 hour for 10 man bg? no, I'm not rerolling horde unless I get a blood elf.
Questing: neat, if there were any left after a few days...
Making a twink: omg yes! no gear done, no faction done, no quests done, you have to tell everyone you know to add another name to their friends list... limited appeal...
Raid with twinks: omg die...