Ultimately, expectations. Gaming is not a passive medium. Its not like a critically panned video games will go on to sell 3m plus, or a hyped up game with great reviews barely sells 1m, this happens in Hollywood on a monthly basis.
However, the word flop is too strong. It happens so rarely that it shouldn't even be considered to describe the performance of a game. Flop should only be reserved when everything, from pre release hype, forum buzz, youtube trailer views, metacritic and ultimately sales are low, recent examples being Medal of Honor and Resident Evil 6.
''Did not meet expectations'' is the best way to describe games overall, example being fan favorite Gears of War 3, which fans expected 6-7m, but it has barely broke 5.6m
While forum goers opinions do not make or break companies figures, it will give the game its lasting reputation.
