Episodes 7,8, & 9 were just a rumor. Lucas has said that he never intended to make such a thing, never considered a script or a plot, and doesn't know where that rumor came from.
As far as Episodes 1,2, &3 are concerned, Lucas originally (in 1975) wrote a script that would be Episodes 4,5, &6 intending it to be one movie. When he finished it, it was way too long for one movie, so he cut it into three parts and made Star Wars, Empire, & Jedi. He wrote an outline for a back story (not a script) that would explain how the characters got to that point, that later would become Phantom Menace, Attack of the Clones, and Episode 3.
So Lucas never really had a detailed script for these three movies, just an outline. That's why he's had problems writing the movies, and why the first two prequels were subpar.
Its a shame, really - because Star Wars IS Americana, and its too bad that he couldn't make another three like 4,5, &6. Lucas has struggled in dialogue writing, and directing (never his two strengths). In retrospect, he should've just produced the movies and gotten a top gun writer and director to do the films. He also needed to delegate some creative control so someone could tell him that things (like Jar Jar, for example) were bad ideas and never should've been a part of the movies.
Both movies have some great, great parts and great ideas that're lost in two bad films. There're parts of Episode I that are perfectly in-line with what Star Wars is: the opening scene on the Trade Federation ship, the awesome light saber duel with Darth Maul (a great character, btw), Sebulba, Naboo, Coruscant, etc. Had Lucas had someone to take the great elements, weed out the bad, and come up with great ideas to replace them, he could've replicated the success of the first three.
As it stands, he has to make a great 6th film to salvage what he's ruined.
