Let's break down your reply.....
Tom Brady is clearly the product of a system, otherwise he would not have made it to the 6th round of the draft. Furthermore, Tom Brady would not have seen the light of day if not for the Mo Lewis hit on Drew Bledsoe.
Peyton Manning came into this league with a tremendous potential, and if anything has shown to be a great QB who cannot win the big game.
Emmitt Smith though highly touted out of college, had the luxury of playing behind one of the best OL of all time. If not for the Hershel Walker trade, he would have been probably a 10,000-12,000 yard rusher. Nothing to sneeze at, but not the all time leader rusher.
You and I will disagree about Zach Thomas. He is a slightly above average LB whose great asset is his coverage skills. You made an excellent observation that he covers the RB and TE, though rarely does he get close to a RB on a running play until after he has crossed the DL. An outstanding MLB makes plays at the line of scrimmage, not 5 yds after on a RUNNING play.