While it's always ideal to have a great game to work with, the quality of the experience doesn't matter one bit if you can't sell it to people. If marketed poorly, a great game can perform below expectations, and the opposite is also true: a bad game can sell like gangbusters when paired with a clever and unique marketing campaign.
Persuading someone to drop £50 or £60 on a game isn't easy, but the more buzz the publisher creates, the bigger its potential audience will be. This is why you'll often see companies pulling all kinds of crazy promotional stunts in an effort to get themselves noticed, because ultimately, any publicity is better than no publicity at all.
From publishers painting pigeons with game logos, to that time when Ubisoft caused a bomb scare by sending a ticking goodie box to an Australian media outlet, the number of bonkers stunts that have been used to advertise video games is shockingly high.
Not all of them resulted in a successful game, but regardless, you have to applaud the creativity and brazenness of the teams involved.