I used to be a fan of AVGN. I don't mean that in a "no fun allowed grumpy face" sort of way. He has fallen under a trend that I notice from most internet video folks. The story always begins with a guy/girl who has a good idea for some goofy crap they can do on the internet, so they start making a couple of videos. At first the jokes are all their legitimate feelings (albeit sometimes over exaggerated). They're not doing it to make money. They're not doing it to harvest fans. They're just doing it as a hobby for themselves. At the risk of sound hipster-esq, I find this to be the best time to be a fan of one of them. Not because they'll be mainstream later, it'll just be that their motivations change.
When that motivation changes you run across a series of issues. The first being they have to rush out new videos. There was a fairly long chain of videos where it felt like James was just doing the same joke over, and over, and over, and over, and over, and over again. You could virtually see himself becoming disinterested in his own stuff. From there he began to branch out into other projects which limited his ability to focus on the character that brings him the bread and butter (hell, he had a radio show on the Opie & Anthony channel on XM for a bit). Every so often James is in a good mood and he does a video where he talks about the games history, and facts about it (in between the usual poop joke) and those videos come off as much better than the ones where he's just swearing continuously for seemingly no reason other than he believes that is why the fans like him.
Less AVGN, and more That Guy With The Glasses based is that once they started basically making it into their jobs they just started to over-script EVERYTHING and it took the genuineness out of everything. They do so many cross over videos at this point that the solo videos actually seem like a sincere treat. You also have the rushed out videos problem here, with LordKat starting to cheat in his "Until We Win" videos as a fairly good example of what happens. Spoony has had a bit of a resurgence of "the old Spoony" since he departed the site a few weeks ago, making you wonder exactly what these guys would be doing each video if they didn't have the "job" of it behind them.
I know this all sounds negative, or at least negative-ish. But I do still watch a good chunk of them and enjoy them (The Cinema Snob is probably my current favorite). I think its just pretty easy to see why somebody wouldn't like them.