[kupoartist]

1. Escapism. Pure and simple "Reality is heavy going, I want to be someone else". People get it to a lesser degree from TV or Film but interactivity takes you one step further, particuarlly first person games. Only Books can match that, and for some people books aren't as accessable. In fact, Escapsim is itself a bunch of positives: You can be who you want to be, where you want to be, when you want to be etc.
2. Games are Art Well good games are at least. The complexity of 3D level design is nearing the point where developers are genuninely going to have to start employing professional architects. Character, Level and Misc design equals anything seen in Costume, Set or Other design departments in Film. Plus, because of the open nature of the Internet as a distribution model, Games are a huge melting pot of creative energy.
3. Challenge There's nothing quite like the feeling you get when you complete your first game. many games down the road, a good game will still give you a sense of fulfillment, that you've achieved something to be seeing the names of all those creative folks roll down the screen.
4. Competition Similarly, Nothing beats beating other people. Sure you have to play online for this, but seeing yourself at the top of the leader board with more frags than everyone else is a great feeling.
5. Co-Operation Just as important as Competition, is Co-operation. Be it a two player split screen triumph over the covenant, or a team of 16 people beating the other at Onslaught, feeling that as a team you've achieved something is a great thing.
6. Community Games News, Reviews and actually the act of playing games encourage a great deal of communication and socialisation. No it's not quite the same as going out in RL with your friends, but it's not to be scoffed at.
7. Feeling Skillful Roughly translates as being able to jump from a high ledge, do a 180 degree turn and plant a bullet between someones eyes at long distance in one movement. Sometimes, you even amaze yourself

That's pretty much it really... Can't think of any more ^^