WoW For the WIN Best game ever made. Can't stand the 12 year old bobby and sue's talking about what they did in arts and crafts afterschool though, other then that great game/pvp.
I play Final Fantasy XI... WoW is too childish and easy for me, I can't stand most of the people on there. Guild Wars is pretty much the same interface as WoW but you don't pay a monthly fee, its fun
City of heroes is awesome when you start playing it. the character generation and power selecting is great. After a (long) time playing it it might feel a bit repetetive. But its great fun.