This is a very old MMORPG made by the Korean company Gravity. It was released in 2002 and is still played by people worldwide although its popularity is decreasing due to various reasons. It also became pretty much free to play, except the VIP servers. This is an MMO that I spent the most time on and will probably spend more since I never get bored of it. That's why I just couldn't resist but writing a review of it :]
The world of Ragnarok takes place in a medieval world with a lot of futuristic elements and mainly borrows from Norse mythology. There are many interesting quests that will keep you occupied. Either defreezing a wizard in an ice dungeon, freeing a girl in Thor's volcano or even unraveling the mysteries of a village full of ghosts, are only some of the quests available to you. However, since it is an old game there are still bugs in some quests and you'll find yourself at a loss since you don't get an explicit quest to-do list like in most MMO's, but instead you have to talk to NPCs (non-player characters) to get more information every time. For the lazy people, there are plenty of guides and walkthroughs out there for RO quests so don't let this discourage you.
You can see the choppy graphics and the fake 3D easily here.