People remember and judge experiences based largely on the peak and the last impression.
We tend to remember experiences by recalling the most intense part (peak) and the final portion (end). This means that people often judge and recall experiences in ways that aren’t consistent with their average experience throughout the game. This is something to keep in mind as a game designer. Often you can find reviewers who will rate a game highly and cite one stand-out experience, or pan a game for a hugely negative experience like losing a game save.
To fully leverage the peak-end rule, linear games should feature a strong climax that is highly polished and surrounded by less intense gameplay and story elements to highlight this peak. Games with more open gameplay should focus on either emergent behavior, which can help players find their own peak, or some unique scripted event that is relatively rare.