It is all very subjective, especially looking at players from different eras.
For me:
Top 5 Bears Players:
Payton
Butkus
Sayers: Controversial pick for many but two-time rushing champion, five-time All-Pro, 22 TDs as a rookie, and over 30 yard avg. as a return man along with HOF for only seven seasons gets my vote.
Luckman
George or possibly Nagurski
I also toyed with Ditka only because of how he changed the TE position but left him off the top 5. Would have him, Atkins, Hampton, Dent, Singletary, Urlacher, either George or Nagurski, depending who I left off the top 5 and probably Grange in the top 15. There is a player my dad and grandfather would talk about, Clyde Turner who I really never heard much on who played back in the 40’s & 50’s. They both said he was one of the better Bear players but I really don’t know much about him or his career.