Darrell Green and Deion were one of the first CBs who didn't play LCB or RCB, instead they lined up on an opponent's best WR.
Plenty of great DTs who changed the way OCs designed interior blocking schemes.
But whenever you see a big butt OT lined up in a two point stance selling out on a pass play, you can thank LT. No tackle in a three point stance could ever block him on passing downs. People talk about LT's sack numbers, but what they fail to mention is during the first 5-6 years of his career, whenever he rushed the QB, he always ended up in the backfield, sack or not. His pressure numbers on pass downs must be close to .850.
This list could be 50 deep easily. Where's Bruce Smith??
And Jack Tatum was a true psychotic at the safety position, the man who inspired the play of Ronnie Lott.
Start at 1960, and for each decade pick your top 10. That should give you roughly 30 to 40 of the best to ever play on the defensive side of the ball.