Ali was honest to a fault. He may have made a better preacher or even his own brand of civic leader even though he loved the ladies too much. Ali used to say boxing was just a prep for what he was going to do next, that was before the damage made that all impossible. He was also very gullible, what else would you say about a guy who would demand his assistant give 10k to a bum off the streets or chew out his bloodsucking entourage out and then feel bad about it? That was willful stupidity because Ali wasn't a dumb man but he was still a mark for a lot of bad people.
Pac as president? I don't know, the religious fanaticism really might have made that difficult. We know he loves the poor though and that might make up for some mistakes, but again, power corrupts. Lots of seemingly decent people got ahold of some power and it warped them beyond recognition.