I don't know enough about Davenport to comment on him, but Datone seemed like he could have been a great 4-3 DE, but the Packers tried to make him a 3-4 DE and then OLB, neither of which he was suited for. And Perry has been borderline decent his whole career, but far from a superstar. I would have expected better from a first rounder.
As for Peppers, he's a hall of fame level superstar who proved he could do the job in any system, even at an advanced age. Hell, I bet if he'd played TE, he would have been all pro there.