Lucas is a World Builder. Probably one of the best in his generation. Right up there along with Tolkien, for example. But he sucks when it comes to the small scale stuff, like character interaction and plot points. It's why Empire is arguable the best SW film, because he only oversaw the general approach to it.
But as a side note, what I don't get about SW now is that you have something like 10+k years of history of the Old Republic to work with. Yet (as far as I know), the only stories deal with the two extreme ends of it, the KOTOR period in the distant past, and the "current age". If you think that, say, a Sith threat emerges once every 500-1000 years or so, that is still 10-20 time frames or so in which to set a new saga, with a new cast and new stories, all within the same galaxy. You could have plots that were nibbed in the bud early on, others that got further, even ones that got to the stage of large scale armed conflict, all without messing with either ends, or disrupting the "flow" of the history of the galaxy. And that is only talking about major events such as Sith uprisings and such. There is a shit ton of smaller stuff that would also be interesting, I mean, it's an entire fucking galaxy spanning 10k years or more.
Damn... now I wish I had some talent to write and build my own universe...