If all this cheering strikes you as excessive, remember: The Lions have never made the Super Bowl. Their fans take what they can get.
It's possible that the cheering also came from smart Peterson fans, who didn't want to see the great one lose a knee this year thanks to the Madden Curse. That curse, by the way? Unless you're counting pulled hammies on the golf course, consider it broken. Sanders doesn't need to worry about breaking a leg like Michael Vick, breaking a foot like Shaun Alexander, or losing his abilities Space Jam-style like Peyton Hillis. Smart move by the fans here.