The greatest chess players in history each get time travel teleported from their prime all into one place, given some time to study up on the latest theory, then rumble in the greatest chess tournament of all time. Rather than debate who would win on objective grounds, who winning would make for a good story?
Morphy wins, revealing that no one during his career had ever pushed him to play at his true strength.
Rather than one of the big name personalities winning, someone often described as having a "universal" style wins, being able to best handle the varied opposition. Spassky or Anand. Spassky en route gets his revenge on Fischer, living up to Fischer's description of Spassky as the one opponent Fischer couldn't completely break on his world championship run.
Someone who was never a world champion wins, revealing that becoming world champion requires more than just chess skill, also political savvy and other social things. Ivanchuk.
Fischer and Capablanca mutually agree to play their games as shuffle chess. Who else joins them?
Someone from the far future wins, defeating even the strongest computer players entered into the tournament. Today's dominance of computer programs is revealed to be just a passing fad; future players have learned to beat them, and in so doing also raised chess ability far beyond what humans and computers have played up til now.