Personally I can't vote for any of those.
ffxi : Total let down, 100% PvE (can't kill each other) The class system in the game is amazing though but it never managed to keep me entertained for more than about a week.
WoW : It is fun for a while then it just becomes this game that you are wondering why you can't stop playing it. If any p2p mmorpg out of the list I might say this one.
eq: "one" of the greatest games of all time, but out dated and it sucks starting out a game that has other players that have been playing it for years.

now for game other people mentioned

Saga of Ryzom are you kidding

Silk Road Online, actually one of the better f2p korean games out there, but very annoying to play international servers, most friends you will make have a 12 hour time zone difference to you, and truthfully, all asian f2p games basically suck and are clones of each other with a few added differences

EQ2, pretty good game, the PvP sucks though, very easy game to get tired of