Marty Stu: Julien Sorel is beautiful, popular/envied and talented to the point of being ridiculous. He is also the center of the story and usually the center of attention. Despite these Marty Stuish traits, the Red and the Black is nevertheless considered a hallmark in the history of the psychologically realistic novel. Together with Murasaki Shikibus Genji Monogatari (which also features a ridiculously attractive, popular and talented protagonist and is considered the first psychologically realistic novel) it demonstrates that you can have a Marty Stu protagonist, at least in some interpretations of the term Marty Stu, and still create great litterature.
Vindicated by History: The Red and the Black was published in 1830; Stendhal stated in letters that he was writing books for the 1930s. It was indeed around that time that he was recognized as one of the greatest French writers of the XIXth century.