Wow, some of you people really don't know film history.... hmmm let's see. Directed, THX-1138 and American Graffiti (both hailed by critics as two of the finest films of their era).
If you're going to blame him for Howard the Duck (which Lucas only came in at the last minute at the request of Universal Pictures due to problems with the production), then you have to give him equal credit for one of the finest films from the 1980s, Body Heat. For that film he came in at the request of director Lawrence Kasdan who was having troubles with the production and more importantly editing the film. Although he is uncredited, Lucas is generally regarded as having a huge hand in the film and essentially edited the film himself.
Yeah, he's sooooo amatuerish
PS Oh, and if you ever get a chance to see his early documentary, "Filmmaker," which chronicles the making of Francis Ford Coppola, "The Rain People," I would highly recommend it.
Yancy