As an old-timer, I have to go with Butkus on defense and Gale Sayers on offense.
The fact that we got both those guys in the same draft still blows my mind!
It blows my mind too. Two Hall of Fame players drafted by the Bears in one draft. Two of the greatest NFL players I've ever watched in my lifetime for sure. I find it interesting to note that the Bears never won a championship during their careers. There were so many Bears teams over the past 50+ years that had great players but no championships. Some of that I do attribute to not being able to figure out the QB position. That changed when we had a healthy Jim McMahon, and the #2 offense in the NFL that year we won it all in 1985. We've had some of the greatest defenses during that span, but without the QB and offense the Bears couldn't get it done.
There is a reason why Chicago Bears fans get so crazy over the QB and offense woes... there is a history here. Lotta pain and frustration watching this over the years. People get angry.