Jay Cutler is not hands down the best QB the bears have ever had. If you are talking about modern style QBs then yes. If you are talking about QBs period, then you can make an argument for Sid Luckman (4 championships and HOF). He was more Tebow than Manning in playing style but he was considered the greatest long range passer of his day.
BMarsh is hands down the best WR the Bears have ever had.