A popular game is a game that everybody knows about. If everyone knows about a game, a lot of people form opinions of it. Some are remotely excited (Montagues), while cynics remain cynical(Capulets).
Then, hype persuades the Montagues to become very excited about the game, and Capulets, when they are told things like "best game ever," become even more cynical. So, there's a dichotomy created where there becomes a league of people so dedicated to a game that they will defend all its flaws, as well as an equally-violent group of cynics, so determined not to like the game, they will ignore its good qualities.
As for why you've noticed that people around the Escapist are like that, it's probably because games like Halo 3 are very popular outside the demographic of "hardcore gamers." So, when the people most excited are people who don't have a great knowledge of video games, the naturally opposing group is the people who do know a lot about them and are the kind of people who'd, you know, sign up an account to a gaming culture website to post on forums...
Well, hope you enjoyed my little theory.
It doesn't cover everything, because every game and the situation around it is different. And, obviously, there are lots of shades of grey between the two groups, but I think that kind of thing happens a lot.
