Wladimir Klitschko and I think it's pretty clear. Lennox had a great jab, but Wladimir's is better. Lennox had the better overall arsenal, but the jab is better from Dr. Steelhammer.
But for me, the whole purpose of a jab is to open up an opponents defence to allow another shot to come in. Lewis followed his jab with a right which was usually devastating. Wlad throws his jab well, but doesn't follow up enough thus making it less effective IMO.
wlad has a top 3 jab of all time imo, some fighters said, that his jab is like a right hand from top 20 fighters. if he throughs is with power, then its his biggest weapon, because his opponents think, wtf, if his jab is so strong, what will happen if he lands a straight right or a left hook, so they go in defense mode
Lennox's jab is better. As another poster said, Wlad often paws with his jab plus Lennox's has been proven to be effective against top-tier competition. Wlad hasn't faced anyone of note that could really challenge his jab in years.
Lewis had a better jab. He used it more effectively against much better opposition. His jab was more versatile, unlike Wlad, he could throw it from more than one angle. Lewis was more accurate with it...Wlad hits the gloves more than the face. Lewis got it in there more frequently. Lewis used it to set up other punches. Larry Holmes' jab is the best.