Ultima Online is a good free MMORPG, and Fiesta online is fun too (and it appeals if you like anime-ish graphics). City of Heroes is fun, but it's pay; and World of Warcraft is supposed to be great, it's also pay but I personally didn't like it.
The Old Republic is going to come out soon and that'll be something to give WoW a run for it's money. Champions Online is one that just came out, I have yet to play it but I've heard it's pretty decent.
Deffinetly MapleStory if you've nevre played it. It takes a little time getting into, but if you stick with it it's really fun! I played for 5 years almost...
There some different types of MMORPG on the site: [url=http://gpotato.com/] So if you think the one is boring then just try another, you only need ONE account to play all the games
I word of advice to anyone who's going to start play MapleStory. Play just long enough to understand the equips and what skills you need for each class and then play on a private server. Not because the real Maple isn't fun; it just takes too long to level up. You'll get bored and quit playing it if you stick with the real server for too long. Unless you have a lot of real life money to spend on 2x exp cards xP