Some would say that George Lucas' lack of activity as a director for 22 years, between 1977 and 1999, is a classic example of wasted talent. I say he didn't waste any talent, because that mousy fuck never had that much to begin with. He read Greek mythology, watched a couple Kirusawa films, then relied on his director buddies, like Spielberg, to hold his hand through Star Wars. Then he sat back and proceeded to collect money from the production of toys and t-shirts for the next 20 years. He's a joker.
And don't forget about the gratuitous releasing, and re-releasing, and re-re-releasing of the first 3 films. Certainly another reason why he borders on con-artist. His first 2 (and only two non-Star Wars) films he directed do admittedly display some talent on his part, but non-remarkable talent, if we're to be honest. In other words, there's not a chance in hell the dude would be revered or remembered, on the scale he is, for only those two works. The cause of his success can be narrowed down specifically to the first Star Wars film, which was created along with the help of Spielberg and Coppolla.
This isn't to say that Spielberg was the only reason Lucas had a successful career. There's also the luck he had with the excellent casting, and Jim Henson's puppeteering. In my opinion those are the three main factors that make Star Wars, episodes 4-6 so special: Spielberg's/Coppalla's help, Jim Henson's services, excellent cast. Maybe fourth, I'd place Lucas' directorial talents. Maybe. Probably not.