On The Office, Jim should have stayed with Karen instead of dumping her for the clearly inferior Pam.
Inferior on what grounds, dare I ask? 
Karen just seems smarter, more career-driven, higher achiever. Jim was a slacker, but she seemed like a good match who could influence him to maximize his potential. Pam, who had little ambition and failed art school, seemed annoyingly insecure (a plot point several times in the later seasons, after they were already married), in contrast to Karen's high confidence.
