Portal 2 is one of my favourite games of all time. It really came down to how every bit of the game felt carefully hand crafted. The way the characters acted, how the story progressed and the emotion they gave off really made a unique playing experience for me. Roughly this time last year two of valve people say down and talked about how Portal 2 went from an idea to becoming a fantastic product. Its an hour long, but is certainly worth watching, and I could only wish that other game developers could have a similar workflow to Valve.