Have to agree, I've never considered Brad Pitt as an actor who plays 'himself' - not like many other actors I could name. Harrison Ford is a prime example, one of the world's most loved actors but it's been a long time since I seen anything resembling acting 'range' from him. To name a few others who always come across the same in their films - Seth Rogen, Matthew McConaughey, Ben Stiller, Hugh Grant, Al Pacino (recently, at least) .....................................
When someone just reads lines off a script in the same accent, manner and style in every film they're in, I don't consider them an accomplished actor. A good actor will convince you they're someone else - Kevin Spacey does it often, as does Daniel Day-Lewis, Johny Depp, Ralph Fiennes, Michael Fassbender, Russell Crowe.
Watch Se7en, then Inglorious Basterds & Snatch, then Troy and finish it off with Fight Club and 12 Monkeys. Then come back here and tell us Pitt comes across the same in all of them. That's only a few examples too, he's very diverse in all his work. It took Pitt a long time to get the respect he was due as an actor, for many of his early years in Hollywood he wasn't really taken seriously (despite his ability) because so many women's magazines and the like had him on their front pages as hunk of the year.