His real persona comes through pretty frequently though, which is why people like him, imo. When he does longer gaming videos, or more serious videos, you can see what he is really like to some degree. Most of his viewers should be very aware that the PewDiePie persona isn't who he actually is in real life, which is a departure from other YouTubers who always have their "TV personality" on while they are recording. Even in his less serious videos, every once in a while he will break from his PewDiePie persona and have a bit of more serious commentary, which makes him seem very genuine, while still being entertaining. The viewers know he is having fun and joking around in his videos, rather than trying to act like he is something he's not.