Prequel Trilogy is like Theatre Drama...

sophistication was his aim and he achieved it, at least on a narrative and writing level. The OT got a lot of derision as being dumbed down fairy tale scifi for children next to the cerebral stuff (2001 et al) and the semi cerebral stuff (Star Trek). Star Wars for many still represents the kiddy franchise that killed quality cinema and created the infantile blockbuster. 

But with the PT Lucas gave Star Wars a narrative and world building backbone by showing how the Galaxy works. This dystopian downfall story showing the slide into totalitarianism is not for kiddies anymore. Palpatine's plot and rise to power, paired with the fall of the Republic, the Jedi and Anakin is Lucas best and most relevant writing by far.

The acting, well, that was always a decidedly mixed bag in both trilogies. But I personally do not see a major discrepancy, both are products of their time and timelines, you have his with every franchise continued after a  hiatus just see Star Trek or Blade Runner.