There's a thread that recommends MMORPGs around here somewhere. Dig down a page or two and it gives like 9,000 opinions on which MMORPG is the best. I've heard good things from all of them, so it's really just personal choice. I'd go with FFXI right now, but that's just me. I'm waiting for World of Warcraft which will come out in 2010.
-Lasereth