MapleStory... I remember that game. Got my account a few weeks after Bera was released and played it for about a year. I lost interest, but it was great fun while it lasted.
Anyway, Nexon/Wizet (Wizet created MS, Nexon merely sponsored it) is supposed to release MapleStory DS sometime in the coming years, although many people suspect that it'll be a sidescrolling RPG rather than a MMORPG.
Anyway, my little blurb on Nexon: Nexon created/sponsored numerous other games such as BnB (an online bomberman clone), some online racing game I remember hearing about somewhere, a FPS called WarRock, and too many MMORPGs to name. I dunno how well most of these games did, although Nexon is making plenty of money and the two games I've played became increasingly popular in the time frame of my playing. Most games and pretty much everything about them are marketed as "casual," right down to their cute website (except for a few of the MMORPGs that have a 3D, fantasy-based, slightly more mature look to them), although from the two games I've played, BnB and MS, you really need to know how to play before you start (in BnB, you'll probably get owned too many times that you'll probably quit if you play too many times before reading up on some tactics and in MS, it's way too easy to "screw up" your character unless you at least loosely follow a guide/build).