Looking at all of the NFL flops on this list who were SEC quarterbacks, it's really almost amazing how few quality quarterbacks have been turned out by the SEC over the years.
You can basically take a quick overview of the 30 years between Kenny Stabler and Peyton Manning and find almost nothing of value, and frankly the returns haven't been much better after Peyton (Quincy Carter, Jason Campbell, Casey Clausen, Brodie Croyle, JaMarcus Russell, David Green, Tim Couch, Tee Martin, Matt Jones, etc.).
Off-hand Jason Campbell is the only league-average starter the SEC has put in the NFL since Peyton that I can recall (outside of Eli), and Campbell has always been just a solid cog on bad-to-middling teams. It's an indictment of evaluation and development given how many talented QB's the SEC has signed over the years. The SEC signs top flight QB's every year, and the MAC is the hotbed of NFL QB talent. Go figure.