Games rely heavily on the main character you play, its simple really a lame rubbish looking character isn’t going to make you want to play as them or be involved in their world in any way at all. However, get it right ad your part way there to getting a game to sell. A good example of creating a successful character in a game is Max Payne; he had everything you could want from his characters archetype. Max Payne was a moody badass detective type who went through the game killing just about everyone in his quest for revenge for the murder of his family. What made him good was the fact he was stylised in quite a dark anti-heroesque way which fitted well with his back story and in turn helped tie him into the game world and connect with the player.
More recently characters such as Altair and Ezio from the Assassin’s Creed series have been well thought through as the story directly ties the player with wanting to hunt down the characters memory and solve the puzzles. As this was cohesive and solid throughout, the game flowed and developed rather than the player being dragged through pointless missions where the best reward is the cut scene rather than the gameplay. Bioshock being a first person shooter and never really showing the characters face, plus the fact the game throws you in the action straight away instantly connects the player with an emotional bond and with the constant struggle the character faces only builds upon that and creates a steady step by step story flow laying smaller parts for the player creating a more thoughtful approach and smoother transition on each part of the game.
Story and character is a symbiotic cycle e.g. a good sounding story can fail if the characters aren’t interesting and unique enough or good characters can fail if the story is weak and full of plot holes. Ultimately games need to start thinking hard about the way they are built. Story and character should be considered a forethought and not an afterthought to special effects and glossy graphics.