I don't believe the analysis is correct, at least not from the angle of sheer story.
The Jerk was the demise of an unlikeable person. It was a demise because, as the tag line said, it was a "rags to riches to rags story". And he was repulsively pathetic, a mean and stupid person who did unkind things. In the end he was ruined, and he somehow deserved it.
Forest Gump was the American dream, but turned on its ear politically and pumped with cinematic steroids. And he was neither repulsive nor pathetic, he was very likeable, honest, and quite sympathetic. He never harmed anyone and only wanted the best for all around him. In the end he was made happy and successful, and he definitely deserved it.
The only common denominator I see is that they were both mentally challenged. Beyond that I see little similarity.