In cognitive science, choice-supportive bias is the tendency to retroactively ascribe positive attributes to an option one has selected. It is a cognitive bias. For example, if a person buys a computer from Apple instead of a computer (PC) running Windows, they are likely to ignore or downplay the faults of Apple computers while amplifying those of Windows computers. Conversely, they are also likely to notice and amplify advantages of Apple computers and not notice or de-emphasize those of Windows computers.
This is one that should seem intimately familiar. Think about how people root for their favorite sports team or back up their political stances. They drastically overweigh the positives and drastically underweigh the negatives.