Although St. Francis of Assisi my have been a great man, even a great Christian perhaps, I would much rather attempt to emulate Jesus our Savior. All men are with sin (including St. Francis), Jesus was without sin, therefore, I will attempt to emulate Him.
No mortal person can fully meet the standards that Jesus set, however, Jesus will forgive our shortcomings, St. Francis can not do that.
The truth is that because Jesus is God the Son, it is impossible to emulate Him, in a direct way, because of human weakness, but when it comes to the Saints who are home with God, they are to be treated like the positive role models they are. They help us to become more like Christ by their good example.