The area where most teams fail is insufficient polish. Cliff [Bleszinksi] always says there’s the first 90 percent of the project, and then the second 90 percent. Because once your game is completely playable and it works, you’re really only halfway. … It takes an incredible amount of tweaking to get to the level of polish where people take your game seriously.
–Tim Sweeney, as recounted by Kevin Dent
As an industry matures, the little details are increasingly critical to distinguishing your products from your competitors’. It’s assumed that you’ll have the basics covered; what people really want to see are polished, well-executed solutions.