If you recall his review of Portal and Psychonauts and stuff, people didn't find it funny when he liked games.
Hence, he has turned the cynicism up to 11. He's a performer appealing to a market that likes it when someone's overly negative about things.
I really like Extra Punctuation, because (when he's not in one of his moods) it lets him genuinely comment on games and talk about issues. Of course, not to the extent of Extra Credits, but it's nice to have a clean divide between Comedian ZP and Critic ZP