Ray's shot single-handedly swung LeBron and Tony Parker's legacies. Parker had an epic close to Game 6 that would have been legendary (especially when paired with his miracle shot in Game 1), while LeBron had just had two crucial turnovers that would have been an albatross around his neck (especially when paired with the Mavs series and the 75 cents joke about not getting four quarters from him).
Game 7, LeBron was epic, and Parker wilted.
It's never just the superstar.. guys like Paxson, Kerr, Horry, Mario Elie, and Ray Allen (even though he's a better player than any of those other guys) inevitably make plays that swing championship series