As a professional Internet, I understand that you may not trust me with your ideas. So if I'm asking you to show yours, it's only fair that I show mine first. So here it is: a motorcycle game. But here's the catch ... it can't be a total piece of s**t.
Virtually every motorcycle game is just a re-skinned car racing game. Sure, there have been a few bulky, incredibly expensive arcade peripherals that have gotten part of the biker experience right, but it shouldn't be that hard to port a motorcycle racing game to a console. The standard controller is laid out a lot like a bike's controls anyway: You have two sets of pressure-sensitive triggers and buttons right next to each other on the underside of the controller. Those are your handlebars. Push on the trigger with varying degrees of pressure to push on the respective bar, and you have a pretty accurate simulation of counter-steering. Just above the triggers you have two buttons. On a bike, they're levers: clutch on the left, the front (or main) brake on the right. One thumb works the D-pad, which could easily control the 1-down, 4-up shifting pattern on a bike. The other thumb rests on the right analog stick, which controls degrees of throttle. For advanced users, the left stick could manage body position, and one of the buttons could control the rear brake. That's it: Those are all the vital controls of a motorcycle mapped perfectly to an existing console controller.
This is the only time having a keyboard/mouse will screw you.