zombie84 said:

They would have gone the same. Actually, they probably would have been worse, since most producer's aren't as good as McCallum and he actually did contribute more to the films in a subtle way than people give him credit.

Basically, the films would have been the same or worse because Lucas would have replaced McCallum with someone who was willing to do what Lucas wanted if McCallum wasn't doing so. That's what Lucas was looking for in a producer--someone to ensure his wishes were carried out faithfully. Sometimes, that's how producers work. McCallum was smart enough to realise this so he didn't push Lucas inappropriately, although he wasn't totally passive. For instance, he warned Lucas about Jar Jar and tried to dissuade him, but Lucas had made his mind up and McCallum realized that's how it would be. He also snuck in an acting coach for Episode III, which is probably why that film has the best performances of all, probably because he saw how embarassing bad Episode II finally turned out to be.

These are interesting timbits of info. It reminds me of Red Letter Media's review in which McCallum is shown with a look of shock after the initial private screening. Then a discussion follows between Lucas, Burtt, and McCallum in which they mention that they cannot edit out the bad parts because they would not have enough material left over for a movie!