There is a book by famed criminal profiler John Douglas called "The Cases that Haunt Us". In the book, Douglas describes some of the more famous historical cases (Jack the Ripper, Lizzie Borden, Lindberg Kidnapping, JonBonet Ramsey) and applies criminal profiling techniques to 'solve' the case (either eliminating some suspects, or pointing out who COULD be the killer, etc.)
In the section on Jack the Ripper, he points out that the killer likely would have been a loner, probably uneducated; the increasing violence and desecration of the bodies showed somone who was loosing touch with reality and would not have been able to 'fit' into society.
Therefore, you can probably eliminate Druitt (a lawyer, even if a 'failed' one), Stephenson (doctor), Prince Albert (royalty), Stephen (a royal tutor), Cream (another doctor) and Maybrick (a merchant). All of these people would have required a certain amount of ability to interact with others, something that Jack the Ripper wouldn't have had.
That leaves Klosowski. However, the fact that Klosowski had been married in the past also casts doubt on him as the killer, since even being married doesn't fit the 'loner' profile.
One of the problems is that many of the people in the Whitechapel area where the murders occured were immigrants, and often had their names changed and/or misspelled. This sometimes makes tracking suspects a little difficult. Klosowski may not have been the murderer, but it may have been someone with a similar name.
John Douglas suggested it could be someone named Aaron Kosminski, a polish immigrant that exhibited a hatred for women, who ended up committed to an asylum shortly after the murders... (Douglas says it was likely Kosminski or someone similar to him).