It is my humble opinion that most of these channels are run by people who have no real sense of what it takes to run a successful business yet, hence why they all copy each other with Minecraft and CoD videos. Couple that with the idea that you can easily make a lot of money off of Youtube by "pwning noobs" and screaming into a mic and you have a gaming-channel bonanza on your hands! I think that most of these people have no clue how much work goes into creating your brand, keeping with quality of both gameplay and commentary, and defining yourself amongst thousands of other creators!
Fortunately, most of these channels give up after a few weeks when they see that the subs don't come rolling in and the cash isn't exactly flowing yet.
I call these people "Youtube-shoppers". People who make a channel with high expectations, take less than an hour to make 15 videos of a popular game, upload them all and notice that nobody seems to be watching them and then leave because they weren't famous by the next morning.
And thank god for these people! Without them the people who put actual effort into a channel would have no way to get noticed or improve their content and acquire some "staying power"! People like PewDiePie don't earn a living by playing CoD all day and using as many profanities as possible in a video, but by maintaining a business, a brand and the associated connections required for that! TotalBiscuit didn't get where he is today by screaming at noobs and pretending to be GoDl!kEpWnaGe on the internet, he did research and presents people with the lesser known games, interviews people in the gaming business and is always working!
That's the thing! To be able to run any sort of successful business these days you need money to spend and a lot of effort!
Is your channel focused on Let's Plays?
How many new games did you buy for your channel this year?
How much have you spent on gear like microphones and capture-cards?
Is your channel a news channel?
How many running subscriptions on journalism- and news outlets do you currently have?
How many people in PR do you know?
Is your channel an Indie game review channel?
How many Indie creators have you been in contact with personally?
How many times have you asked them for a review code or gave them feedback on that Beta you entered?
I notice that I'm starting to rant a bit at this point, so I'll stop it here. But know that not all gaming channels are like this, and that not all gaming channels deserve the bad reputation that they get from being focused on videogames!