I think they were closely matched. It seems that Kame was getting more frustrated as the fight went on, but they seemed to have different mentalities when approaching the fight. Kame wanted to quickly get rid of Goku and teach him a lesson, not believing some brat, although Goku he is, could compete with him blow for blow. Meanwhile, Goku seemed to be excited with fighting such an awesome old geezer and wanted to enjoy the fight as much as possible. It seems their main gap was regarding their stamina, as Jackie was tiring faster. It's also worth noting that when the fight was over, Goku said he couldn't defeat Jackie Chun either way, spoken to Kuririn. Could be only Goku being humble with the man he was looking for, but I think that speaks to how evenly matched they were. When Goku got a lead over him and almost knocked him out bounds, we have to remember too that Jackie just had used his FP KMHMH to destroy the moon and was winded, which he makes not of.