Its got to be said, characters can make or break a game, or any story. After all, they are the ones you control, listen too and interact with. Obviously TV programs and films are different in the way that you do not interact, plus the fact that a film only has 2-3 hours to introduce, develop and explain a character, where as books, games and TV programs can take longer.
The first games to really bring characters into them were games like Full Throttle. They actually used voice actors and were able to develop them which added so much more depth to the game.
I also find it interesting to play Grand Theft Auto 3, and to notice how the main character never speaks a word! But yet the story still keeps you hooked. I think this is due to the characters around you and how they have strong but different personalities.
When I play a game or watch a film, the script can really make a difference, for example the film Enemy at the Gates, a film about the rise or a russian sniper during WW2. It had an epic story line and battle scenes but was let down by a terrible script in my opinion (and Jude Law).
Bad acting can make just as much difference. Take Assasins Creed. Altair, possibly the coolest looking and moving character I've ever seen in a game, but was played by some American (in the Middle East!) who sounded more wooden than my desk, and weakened the character as a result.
Though, I think that it is very important to have convincing and nice looking characters, because first impressions really count. Whether you think it or not, your mind will automatically asses something (or someone in our case) within the first few seconds of seeing it, and make a judgement. It's then up to the writer and actor to build their personality and change that persons mind to how they want you to see that character.
So when you first saw me, you would have made a subconscious decision on whether you liked me or not.....I wonder if its changed?