I think that looking at a leader takes time especially when you are examining a president. For instance we have no idea what Obama’s current policies will do in the long run so therefore we can necessarily judge them finitely as good or bad.
I know judging things years or even decades later gives us an unfair advantage, hindsight being 20/20 but ultimately what makes decisions either good or bad is how they pan out in the long run.
With that being said I always answered this question, at least on a President level, with Lincoln. Unlike some other leaders who had greatness thrust upon them Lincoln knew exactly what he was walking into the moment he was elected and handled it pretty well. Also if any of you out there are into a good history read take a look at “Team of Rivals”. The book shows how Lincoln viewed and welcomed different opinions in order to make informed decisions.
As for people right now, I’ll tell you in ten years… not fair but I’m an ends person and not too concerned with the means (as long as it’s not outlandish).