A lot of people express that opinion. It never gets any less stupid to hear. Discussing a game's positive and negative qualities, comparing it to other games in its genre and in the past, and expressing your opinion in a clear concise manner are important to reviewing videogames.
He finishes the games he reviews, what the hell matters beyond that? Also, protip: Most people playing games also are "bad" at games. If they weren't, normal modes wouldn't be so easy in games these days.
I mock Brad's performance sometimes because it's fun, but I'd never question his qualifications as a reviewer or journalist based on Quick Looks. And being bad usually has very little to do with why Brad dies in games anyway. It's usually indecisiveness and running around while discussing the game or showing off certain aspects (see the most recent RE5 video or the Dante's Inferno QL for obvious examples). Somehow I doubt that when he's not on camera he's doing the same things. Hell, sometimes he even seems to be getting worse so it's probably our fault :lol
edit: Nothing above was necessarily directed at any individual person, even if I seemed to imply otherwise with some of my word choice. I could edit it, but eff that. I'm too good at games to bother writing well.