MapleStory, maplestory is great for killing time, and is great for meeting people. Some of the cons of maple that it is, well, 2-D, and alot of people don't like that, it doesn't work to well on Vista, and, theres hacking, that drives people away. But a con is, it's just awesome, you don't relaly even need to level up to play, you can just log on to talk to friends, that is why it is better. Sometimes, i'll spend the WHOLE day chatting with friends on maple, without worrying about a monthly payment.
WoW is to large of a game, and theres a monthly requirment, if you don't pay that requirment, you can't play. The cons of this is that, you have to pay, the game actually isn't "free" to download and keep. The pro's on this is that it has a nice 3-D, and doesn't really have any major glitches, there might be an occasional one, but, yeah.
Runescape, runescape is probably one of the best games you can play....if your comp sucks MAJOR butt cheek. The Pro's are that it has low requirment, no download required, and usually doesn't burn your computer out. The MAJOR con of this is game, is like most games, the clicking, people REALLY don't enjoy that, another less major con of this game is that, the 3-D is sorta sad for a game thats been in development for over the last 8 years; you can't clearly see a face, and theres still glitches. (Lots to say the least.)
