It's very difficult to pick greatest at positions when there are varying levels of eras in NFL history, and stat counts like sacks, tackles, etc. were not officially tracked. You'd have guys like Deacon Jones, Joe Greene, Merlin Olson, Donald, White, etc. in contention for best DL with two awards - DE and DT/NT. Then guys like Butkus, Ham, Singletary, LT, Seau, Lambert, Lewis, etc., at LB with two awards - ILB and OLB. When it comes to the secondary it's probably hard for today's fans to pick the best CBs and FS/SS. For me, there is no safety in Ronnie Lott's class, all others are a tier below, and he was all-pro at CB before moving to safety. Pre-90s CBs like Hayes, Renfro, Blount, Willie Brown, Lane, so forth were studs.