LOL! I thought about that too. One hopes that by the time they get to Major the incompetent ones have weeded themselves out, while the bad ones are moved to positions where they can't hurt anyone.
Wesley Clark disproves your theory. General George Casey disproves it again. And of course General George McClellan seals the deal. General Petreaus, who spent eight years studying and developing counter insurgency techniques steps into the breach. Somehow this country always manages to find the right person, at the right time. We don’t always make the right pick, but come crunch time, we do. Is someone looking over our shoulder, when it counts?