I guess it all depends how you view things. Jackson wasn't sick, dead, etc. - He was still healthy and able, so I don't think it's wrong to speculate on what he could have done (similar to guys who missed time in the prime of their careers for military service. If the stories are true, he took gamblers' money (definitely a no-no), but did more than anyone to help that team win the Series anyway. A lot of people from that era considered him to be one of the elite hitters.
This is why stat geeks alone should not decide HOFers.