Well Gameforge has Metin 2 and Nostale. Which are supose to be good,havn't played Metin myself. Jagex has Runescape (makes you feel unmature when you play it though=/). NCsoft has a bunch of good games (Guild Wars woot).
Then theres a bunch of time passers like Fallen sword & Dragon Fable.
Also theres LoTR online Which is also suposed to be good.
Thats about my knowledge of the games atm. Hope any of this helps=D