Twenty years ago, the idea of levelling up in a game was confined to a very specific genre: the role-playing game, whose systems were based on pen-and-paper games such as Dungeons & Dragons. Today, you can still level up in an RPG such as Dragon Age, but you can also level up in far wider variety of games, from sports titles (think of the Be A Pro mode in numerous EA Sports games) to FPS games such as Bad Company 2 to driving games like Dirt 2. The vast majority of modern games monitor, quantify and reward your skills in a way that would only have been familiar to the biggest geeks in the 1980s.
While gamers often lament a lack of innovation in games, game mechanics change as rapidly as styles do in other forms of media - so while levelling has gone mainstream, the health bar appears to be on the way out and very few games these days features lives or continues. The question then, is why is levelling up so popular?