Jade Dynasty
Much like the name suggest, it has an Asian-themed look and backstory. I've played for maybe two or three hours today and have already gotten to level 22. Some places of the game feel a bit empty though and too spread out, but it has an path finding system that will automatically send your character wherever they need to go for a quest, so you can set it and go do something else for a bit. Overall, it's fairly fun to play, nothing truly amazing here, but it does look good and move at a very brisk pace. Not the best, but worthwhile.
Vindictus
This game is just so much fun. The combat is really rewarding and deep, it's so much more than just massing the number keys until you win. Fighting bosses is really great too, especially with three other people [four is the max for the instanced dungeons]. Also, doing various things in the game, some optional and some not, get you titles that you can wear above your name, they also give you all kinds of stat bonuses just for obtaining them. The instanced dungeons seem a bit simple at first, but as you get farther into the game it becomes clear that they're actually deceptively simple. You see, to fully "complete" an instanced dungeon, you have to fulfill various criteria, which can include dealing a death-blow kick to a boss or collecting certain items. Some quests require you to get a certain score on a dungeon before progressing. This is a really great game and, since it's free, there's absolutely no reason not to try it out.
Alliance of Valiant Arms
It's basically Counter-Strike the RPG. You pick one side or the other and try to accomplish goals while the other team tries to stop you and there's lots of shooting and blowing up. There's also a ton of things to unlock or purchase with actual money. It's fun, but feels a bit stiff on the control side.
Atlantica Online
Yet another MMO, but this time with turn-based combat! Too bad the combat is boring as heck and totally shallow. Apparently this one is supposed to be really good, but I just don't see it. Maybe I need to play a little bit more, but I haven't seen anything in the first hour or so that's going to draw me back for more.
ACE Online
Flight simulator MMO, now there's a new one. It's still got all the typical grinding and monster chasing, but now with you flying a ship and fighting enemies in realtime with lasers, machine guns, and rockets. The graphics aren't particularly great, but it does manage to be a pretty fun game.
Updating ranking:
1. Vindictus
2. Lord of the Rings Online
3. Need for Speed World
4. Dungeons & Dragons Online
5. Aika Online
6. ACE Online
7. Alliance of Valiant Hearts
8. Jade Dynasty
9. Atlantica Online
10. Monster Forest
11. Mabinogi
12. Shaiya
13. LaTale