I always hoped for a sequel to Blur.
The most fun game I've ever played online. When the multiplayer demo released on xbox live, a couple days before my dissertation was due, i decided to take a 30 minute break to try the demo.... this ended up with me playing the game for about 10 hours that day.
Compared to Mario Karts (as in style it was most comparable to karting games) it was a lot more frantic experience with 20 players a lot faster pace and having realistic locations/cars. Sadly the studio was closed, but for me it will always be the most underrated game I've played which I blame due to a lack of marketing, if a friend hadn't told me about the demo I would have never even heard about the game anywhere else.