I've been with my girlfriend for over two year and so far I'd like to say that we love each other a lot. We also like to play video games a lot. And we been playing a lot of online games. Unfortunately for me I can play as much as her since I have to work. So... Since this is really painful for me to continue (sorry everybody.. ) my girl has been cheating on me with a friend of ours online... and has developed feelings and affection for him. I don't know what to do. I still love her and I want us to still be together but I just don't know what her feelings are for me and the other guy...

She's cheating with him online? You're going to have to define that a little better.

Regardless if only one part of a couple, being you in this case, wants to be together then they're not going to be together. No matter how much you want to convince the other one otherwise. This is why break ups hurt so much. Have you sat down and talked to her about this? How much of this is known and how much is suspected. There are a lot of relationships that fail due to misscommunication. Please talk with her and figure out what is going on with her and this other guy but more importantly her and you.

I often see people come here and say something like this:

I've been with my girlfriend for over two year and so far I'd like to say that we love each other a lot.

But then they follow it up with something like this:

my girl has been cheating on me with a friend of ours online... and has developed feelings and affection for him.

It can't be both ways.

Sit down and talk to her about why her feelings changed and if she is even interested in trying to work something out, if she is, then you are going to have to ask for her to stop interacting with this friend. If she is interested in him, more than she is wanting to stay with you, then it will be time to stop wasting your time and call it quits. Why is she playing online games so much? Does she not work? Maybe getting her actions straight will push for less time talking to this guy during online gaming?

If you are correct, she is emotionally cheating, this usually ends up in physical cheating and break ups. But be careful! Do not nag to her about it, you have to be better than him, if you start foul mouthing the guy, she will feel offended and automatically side with him, putting you at a disadvantage. Toughen up, make her realize she likes you not only for the games, try to spend more time with her, take her out to a trip, or buy flowers, take her out for dinner, and the next day, when she's in a good mood, tell her you don't like her getting close to other guys, because you want her to be with you, because she is important to you.
Play it how you like, but don't tell her that she's cheating in any way, she might not see it that way, although it's true, most people aren't aware of emotional cheating. So just make yourself feel important to her, loved, and happy, and you have nothing to worry about! :)

If your relationship with anyone has more to do with games and or anything to do with being online, it is not a relationship, try living in the real world and have fun doing real world things.