I will say for this generation, Oscar showed an ATG jab the night he fought MA Gonzalez. He had a fantastic one overall.
Quarteys Jab > Oscars. Of all time I would go with Ali. I would venture Ali's jab was probably the best combo of accuracy, power and speed of any jabs in the history of boxing.
Ken Buchanan Sonny Liston Larry Holmes Oscar De La Hoya Carlos Monzon Thomas Hearns I really like Pavlik's jab from the current crop, accurate and heavy. Bernard Hopkins has an underated jab.
Dariusz Michalczewski had great left jab, that punch was opening the way for big right or just destroying opponents face. Shame that he never fought Roy
What about Rafael Marquez? He did some serious damage to Vasquez with it. Its also very straight, quick and powerful. I love that jab.
OK, since noone else feels like saying it, Whitaker is among the very top jabbers of all time. I feel he'd out-jab pretty much everyone around his weight at his prime. Mijares is probably the best today.
I didn't like it him but he did have a good hard jab. Virgil Hill also had an excellent jab. Then there are the usual candidates like Larry Holmes, Lewis but I would not inlcude Waldo in that list though.
Not necessarily the best... but I love Johnny Tapia's jabbing abilities. That shotgun jab always dictates the action in his fights. I love how he isn't ever left susceptible to counters with it. Also, how he'd roll into the fighter and allow it to be the war he wanted it to be (or inside fighting) I thought was an excellant tool to his arsenal.