It's tricky to call Second Life a game. You win a game. You compete in a game. A game has some sort of objective. There's none of that in Second Life - it's simply another place to create, or hang out, or escape.
Nissan managed to change that. If you visit Nissan's Second Life island, you can IM the character Toast Alicious (who really looks like a piece of toast) for the password to the Nissan vending machine so you can get a Sentra for free (I had to pay for my Ben Folds t-shirt, but I get a free car - the SL economy hardly makes sense). Then I drove around, shifting gears, and it goes FAST. Second Life turned into a video racing game. I need to get some friends in there and set up a tournament - it could even be more fun than MarioKart. Click the photos for a better view.
Second Life was anything but a video game before, but Nissan quickly changed that. Though I'd imagine soon we'll have virtual world road rage.