What Makes a Game of the Year?

Pixelgate writes:

''With the end of the year drawing ever closer, people are beginning to create their ‘Game of the Year’ lists. As always, the majority of the time, there is always a group of people who will question anyone’s choices. This is all fair and good, but everyone has their reasons for selecting a game–or games–as the best of that year. But what makes a game of the year? Is it based purely on merit or quality and technical finesse? Is it how successful the game is both commercially and critically? Or is it something more personal?''