This video shows a complete run of the Nürburgring's Nordschleife course, widely rated as the best damn race track in the world. On the bottom screen, a real driver, in real life. On top? Gran Turismo 5.
The real driver is Denis Malevanyi, a part-time veteran of the course. He's driving the exact same car as is being driven in the GT5 video, a BMW M3 E92.
While it's easy to pick the differences between the two clips, like the colour range and misplaced background scenery in the video game, it's also worth noting the stuff Gran Turismo 5 gets right. Like, pretty much everything to do with the track itself.
[thanks MtlAngelus!]