Mavlock is completely right. Most of the rage in gamers stems from a feeling of entitlement.

Interestingly enough, this isn't limited to video games. I recently opted in to beta test new versions of the Twitter app for Android, and I stumbled upon some user reviews; the majority of them being among the lines of "FIX THIS NOW". 

In a more video game-related manner:

I'm going to take an example from 2012-recent. Enter Diablo III. The rage from gamers can be felt constantly, anywhere on the forums and website. There's not a single thread without complaints about the game, not even on news posts on the main page. Even on the recent announcement of the Reaper of Souls expansion, people raged, complained and whined about the game not being exactly what they wanted it to be. When Jay Wilson quit the D3 development team, I read through the forum thread attached to the new post. Over 70% of them were hate posts. I'm not going into detail, but suffice it to say that it wasn't pretty.

So where does all this rage come from? I personally think it's a mix of entitlement, and bandwagon practices. The more people join in on the discussion, the more exaggerated their opinions become. 

I'm happy to see there's a community that acknowledges this problem, and does not hop on the bandwagon.